Planescape Planescape: Fantasy Taken to the Edge (5e conversion)

[h3]HARMONIUM ("HARDHEADS")[/h3]
Peace is our goal. But if it takes a little war to get others to see things the right way - the Harmonium way - so be it. That's how we'll reach our golden harmony.
Prerequisite: Only Lawful-aligned characters can join the faction.
Benefit: You can cast charm person as a 1st level spell once per long rest. In addition, you can spend Inspiration when casting charm person to invoke one of these extra effects: either the target does not realize you charmed them, or you cast the spell as if using a spell slot of the highest level you could cast (use the warlock table as a guideline).
Restriction: There are two things which the Harmonium considers treasonous - disobeying just orders from a Harmonium superior, or initiating wanton violence with no intention to use it to arrive at peace. Should you betray your faction's beliefs you cannot gain Inspiration until you atone or otherwise prove yourself to your faction's cause. 

Knight of the Measure (feat)
Prerequisite: Harmonium faction membership

Having proven yourself as a believer in peace, you undertake officer training in Arcadia, learning advanced methods of peacemaking and peacekeeping. Upon graduation you were elevated above the common Notaries as a Knight of the Measure, empowered to interpret the commands of your superiors in the field as a faction operative. You gain the following abilities:

• During downtime you may meditate on the nature of peace; each day you so meditate in a region, there is a 1% cumulative chance that all violent conflicts are subdued in that region. Additionally, during downtime in a settlement where you can contact Harmonium subordinates, gain the benefits of the Retainers background feature of the Knight variant Noble background (see PHB); these retainers are low-ranking Notaries in the Harmonium.
• Your saving throws against fear and emotion-related magic and effects are advantaged.
• Once per day you can cast command as if using a spell slot of the highest level you could cast (use the warlock table as a guideline). If you're a cleric or paladin add command to your spell list.

[h3]MERCYKILLERS ("THE RED DEATH, SONS OF MERCY, SODKILLERS")[/h3]
Justice is everything. When properly applied, punishment leads to perfection.
Prerequisite: Only Lawful-aligned characters can join the faction.
Benefit: Once per long rest you can cast zone of truth as a 1st level spell. In addition, you can spend Inspiration to deliver a blow for justice against a known criminal, turning a hit into a critical hit.
Restriction: Mercykillers who commit crimes, who let the guilty go without justice, or who present false testimony against the innocence betray their faction; should you commit such an offense you cannot gain Inspiration until you atone or otherwise prove yourself to your faction. 

Justiciar (feat)
Prerequisite: Mercykiller faction membership

Swearing to pursue an escaped criminal, you undertake a ritual witnessed by other Mercykillers in which you sign a blood oath, are magically linked to your quarry, and are given a magical warrant of holding or blood of justice to complete your task. As a Justiciars you are given greater leeway under the normal strictures of the Mercykillers and are allowed to break minor laws in pursuit of bringing the criminal to justice. A rare few Justiciars devote themselves instead to emancipation the wrongfully imprisoned and proving the innocence of the wrongfully accused. You gain the following abilities:

• You have a flawless direction sense to your bonded quarry, which spans across planes and is unaffected by all magic or spells. Likewise, your quarry becomes aware of this bond; if they are a criminal they are filled with dread, while if they're wrongfully accused they are filled with hope. This ability requires you to have a piece of evidence from the crime the quarry committed or an object of significance to the quarry; without this focus, your direction sense does not work. During a week of downtime you may change who your quarry is via another ceremony, though only if the situation with your previous quarry is resolved.
• If you pursue a criminal, you receive a warrant of holding which, when used against your bonded quarry, casts a hold person spell against which their saving throw is disadvantaged and which functions even against creatures normally unaffected by such magic. The magic of the scroll is only expended if your quarry fails their saving throw. If you seek to free someone wrongfully imprisoned or falsely accused, you receive a vial of blood of justice; a creature imbibing the blood or wounded by a weapon coated with the blood must make a Constitution saving throw or be poisoned and consumed by overwhelming guilt, confessing any and all crimes they've committed in the last 24 hours. When you take on a new quarry, the Mercykiller faction will replace your warrant of holding or blood of justice.
• During downtime you can meditate on Justice; for each day you so meditate in a region, there is a 1% cumulative chance that Indifferent and Friendly NPCs in the region are mostly honest and the justice system works without corruption (or perhaps the judges seek your input for proper punishment or rehabilitation of the accused).

[h3]REVOLUTIONARY LEAGUE ("ANARCHISTS")[/h3]
The status quo is built on lies and greed. Crush the factions. Break 'me all down and rebuild with what's left - that's the only way to find the real truth.
Prerequisite: Lawful-aligned characters don't join the Anarchists because of their doctrine of overthrowing "the power."
Benefit: You can automatically pose as a member of any other faction without being detected; you don't gain special abilities that are spell or training related (such as a Xaositect's babble or a Cipher's initiative bonus), but you do benefit from abilities related to position or title, including access to the faction's headquarters. In addition, you can spend Inspiration as a reaction to perfectly conceal your thoughts and motives; whoever was attempting to gain insight into you receives whatever information you choose or merely gets a muddled result.
Restriction: You must donate 90% of all treasure gained to the revolutionary cause or to the oppressed (though in no case can it be given to another player character). Anarchists cannot hold public office or noble title, own a business, or take part in anything that would tie them to the power structure; should you betray your faction's beliefs in these ways, you cannot gain Inspiration until you atone or otherwise prove yourself to the faction cause.

Anarchist Cell Leader (feat)
Prerequisite: Revolutionary League faction membership

After months of sincere opposition to a regime or authority, you inflicted a crippling blow in the name of your faction and were elevated as a leader of an Anarchist cell, organizing efforts to "fight the power" between multiple resistance cells. You gain the following abilities:

• You have experience working in the shadows. Gain proficiency in one of the following: disguise kit, forgery kit, or thieves' tools. Also, gain the Criminal Contact feature from the Criminal background (see PHB).
• You are under the effect of a permanent nondetection spell against divinations cast by Lawful spellcasters.
• During a downtime you can organize a resistance cell to fight an authoritarian regime or other authority you deem unjust. This gives you a cumulative 1% chance per day to intercept a cominque, stymie the regime's communications, or perform some small act of sabotage so long as you maintain active resistance while remaining undiscovered.

[h3]SIGN OF ONE ("SIGNERS")[/h3]
The multiverse exists because the mind imagines it. The Signers - it could be any Signer - create the multiverse thru the power of thought.
Benefit: Your saving throws against (and attempts to disbelieve) illusions are advantaged, as you believe all the world is created from within. In addition, you can spend Inspiration as an action to invoke the power of imagining to effect minor coincidental changes to your environment, like an unexpected door providing a much needed escape route or a street crew forgetting to light a lantern; as a rule, these changes cannot change what has already been established in the scene, and the DM should have final say over what is an allowable coincidence.
Restriction: You suffer disadvantage on Insight checks due to your egoism interfering with understanding the motives and feelings of others. Signers reject materialism, and anytime you indulge in rampant materialism or disregard the power of the mind to shape reality, you cannot gain Inspiration until you atone or otherwise prove yourself to your faction's cause.

Signer Reality-shaper (feat)
Prerequisite: Sign of One faction membership

Predicting a significant future event and ensuring it came about earned your place as a high-up in the Sign of One, where a council of peers elevated you into one of the Signer "think tanks" and empowered you as an independent faction operative to assist the Factol, guard faction outposts, assist and oversee lower-ranking Signers. You gain the following abilities:

• When you use Inspiration to invoke your Signer imagining ability, you can emulate any spell of a level you could cast as if you were a spellcaster of any class. Doing so requires an imagining check - a Charisma check equal to a DC of 10 + the level of the spell. If you succeed the spell is successfully emulated. Each subsequent imagining check you make in the same week imposes a cumulative -5 penalty on your Charisma check. If your check result is 1 or less, roll on the Imagining Mishaps Table.
• Gain an animal companion or NPC henchman (CR 1/2 or less) or a common magic item that you imagined into being.
• During downtime you can engage in lucid dreaming; each day you lucid dream there is a 1% cumulative chance that you gain the benefits of research or training while you sleep, and furthermore that some aspect of your unconscious manifests in reality (e.g. a person or creature from your dreams).
  [sblock=Imagining Mishaps Table (d4)]
  1. You imagine yourself out of existence until someone casts a wish to bring you back or another Signer imagines you back into existence.
  2. You suffer a level of exhaustion and cannot use your [imagining] power for the remainder of the week.
  3. You become an ethereal version of yourself, reducing your maximum hit points and damage by 50%; you may try once per day to return to reality with a DC 15 imagining check.
  4. Your imagining has an unintended effect, as determined by the DM. This could include the spell backfiring or a coincidence working against your party, for example.
  [/sblock]

[h3]SOCIETY OF SENSATION ("SENSATES")[/h3]
To know the multiverse experience it fully. The senses form the path to truth, for the multiverse doesn't exist beyond what can be sensed.
Benefit: You gain darkvision 60 ft (or increase the range of your darkvision to 120 ft if your race grants it to you) and proficiency in either Insight or Perception (your choice). In addition, you can spend Inspiration to use a sensory touch during a minute of quiet reflection, touching an adjacent creature and transferring one of your HD worth of hit points (including your Constitution modifier) to them as you open yourself to their pain; at 4th level you can transfer up to 2 HD, at 8th level up to 3 HD, at 12th level up to 4 HD, at 16th level up to 5 HD, and at 20th level up to 6 HD.
Restriction: Sensates embrace new experiences, so long as there is no obvious deadly peril. Should you refuse a new experience, you cannot gain Inspiration until you atone or otherwise prove yourself to your faction's cause.

Master of the Senses (feat)
Prerequisite: Sensate faction membership

Entering the upper echelons of Sensate leadership requires you to present three rare sensations for recording on recorder stones, and to explain what you have learned from these experiences to your Sensate sponsor. Thereafter you are appointed as an independent faction operative and spy. You gain the following abilities:

• You can establish a sense link with an adjacent willing or restrained/incapacitated creature during a minute of quiet reflection. If they are unwilling, they get a Wisdom saving throw (DC 10 + your proficiency bonus + your Charisma modifier) to resist. Once the link is established, you gain the benefit of a clairvoyance/clauraudience spell centered on the target as long as you maintain concentration (up to 8 hours), though you and the target must remain on the same plane. If you use sensory touch on a creature you are sense linked with, you can also transfer a disease, poisoned condition, or minor curse from them to you.
• Your knowledge of lore rivals bards from your extensive travels. Apply half your proficiency bonus (rounded down) to any of the following checks you make in which you lack proficiency: Arcana, History, Investigation, Nature, or Religion.
• During downtime, you can perform a sensory meditation; for each day you so meditate in a region, there is a 1% cumulative chance that people (NPCs and PCs alike) will notice subtle details they would otherwise miss, avoiding an ambush at the last second or sensing poison in a goblet, for instance.

[h3]TRANSCENDENT ORDER ("CIPHERS")[/h3]
Action without thought is the purest response. Train body and mind to act in harmony, and the spirit will become one with the multiverse.
Benefit: You gain a +2 bonus to initiative. In addition, you can spend Inspiration to enter an action trance as an action; this trance lasts for up to one minute, and while in the trance you always win initiative ties, can take reactions even when surprised, and gain advantage on Acrobatics and Athletics checks.
Restriction: Ciphers act without hesitation. Should you pause to consider or debate a pending action, or waver in your course of action, you cannot gain Inspiration until you atone or otherwise prove yourself to your faction's cause.

Master of the Mind (feat)
Prerequisite: Transcendent Order faction membership

After receiving recognition from your peers, you undertake several months of solitary training to attain a state of thoughtlessness and pure action. Once a council of the Order's masters deems your mind and body to be one, subject only it the cadence of the planes, they give an enigmatic test of your reflexes and intuition, and when you pass you are admitted as a Master of the Mind. You gain the following abilities:

• Increase your initiative bonus to +4
• Entering an action trance no longer requires any action on your part; you may automatically enter the trance when initiative is rolled. In addition, while in the trance your saving throws against mind-affecting spells and effects (like charm person, a monster's fear aura, or a harpy's song) are advantaged, and you are immune to detect thoughts and other forms of mind-reading.
• During downtime, you can enter a state of deep meditation on the cadence of the multiverse; for each day so meditating there is a 1% cumulative chance that you gain precognition of some event at the DM's discretion as if you'd cast divination.

[h3]XAOSITECTS ("CHAOSMEN")[/h3]
Chaos is truth, order delusion. Embracing the randomness of the multiverse, one learns its secrets.
Prerequisite: Only Chaotic aligned characters can join the Xaositects. Because purple fizzle my wozzle.
Benefit: You know scramblespeak, the secret language of Xaositects, and you have an instinctive sense for where to find lost items; this requires making a Wisdom check against a DC determined by the DM. You can't repeat this check until the item moves, and this sense for lost items doesn't apply to items that were deliberately placed somewhere, only to those misplaced thru the forces of chaos. In addition, you can spend Inspiration to invoke the babble spell. Spellcaster Xaositects add the spell to their repetoire at 5th level.
Restriction: Xaositects don't found businesses, build strongholds, raise armies, or undertake any other action that requires long-term organization and discipline. Should you take such distinctly un-Chaotic action, you cannot gain Inspiration until you atone or otherwise prove yourself to your faction's cause.

Xaos Boss (feat)
Prerequisite: Xoasitect faction membership 

There's no clear path to how one emerges as a Xaos Boss of the Xaositects. One simply has to come up with an idea that other Xaositects take to heart, have enough leadership skill to manage them, and enough wisdom to cultivate a deeper understanding of chaos theory. Xanxost suspects little blue butterflies are involved. Yum. You gain the following abilities:

• You can cast confusion once per long rest.
• You gain a random magic ability usable by spending Inspiration. This may be a 1st - 3rd level spell that reflects your character's personality, it might be the ability to duplicate the effects of a magic item with a random component (e.g. a wand of wonder), or it may be a certain roll on the Wild Surge Table (see Sorcerer in the PHB). Whatever the case, the DM should have the final say on what is allowed. Every so often (perhaps weekly or after each adventure) this ability randomly changes or behaves unpredictably.
• During downtime, you may meditate on the nature of Chaos; for each day of such meditation in a region there is a cumulative 1% chance of some random event occurring, particularly one that confounds conventional cause-and-effect, such as unseasonal weather, an enemy sending a gift, etc.

Babble
3rd level enchantment
Casting time 1 action
Range 30 feet
Components V, S
Duration 1 hour

All creatures within 30 feet of you that can hear you must make a Wisdom saving throw, and if they fail they find all their attempts at spoken language to come out as garbled nonsense. 

OK, thats the main 15 factions! Hmm. Hit a couple snags in my conversion...

1) What should an Anarchist be able to use Inspiration for?

2) How should a Signer be able to use downtime for a "1% cumulative chance..." ability?

Moving a piece of land from one plane to another should take a massive effort, like 10 Inspiration points per square foot with a minimum investment of 1,000 points just to get started...

Hi, only just registered here to comment on this. I've both played in and run Planescape in the past. To begin with it was as the modules were being released.

To try to help answer your questions:

1) Maybe Anarchists can spend their Inspiration to act against the 'laws' of the plane they are on?

2) What about Lucid Dreaming let the Signer carry out a learning downtime action at the same time as another downtime action, at half rate: they're able to study when they sleep.

As a suggestion, since factions are all about belief, why not make joining a Faction as simple (and as hard) as having the correct Ideal: Anarch, Cipher, Hardhead etc. It means that you don't have to have something else to track on the sheet.