This is a bit longer of a reply, but I'm glad you pointed a few of these out to me. A lot of them are just the result that we trimmed a lot out for the teaser, so the answers are in the full text, but I'll answer you here for fullness's sake.
Magical boons: Do the energy resistance boons stack with each other?
Very little stacks in this system, with the main exceptions being Evoke and Heal damage and curing. I'll add in a short line to each of the energy resistance boons (and the greater animagus one) to say that if you pick a higher-powered boon for the same element, you can swap out your old boon for something else.
Signature Spells: When can a character choose to change their signature spells, every day, level... ? The teaser for Lyceian arcana implies that they can be changed by saying that a member of that tradition must keep one constant.
Changing your signature spells is doable no more than once per game session, and takes your character 8 hours. The specifics of the ritual, study, procedure, etc. are left up to you and the GM to determine, but since signature spells are designed to speed up the game, we suggest a limit of only changing them between game sessions. Of course, if you have a weird session, where the first half is one day, and the second half is two months later, your GM should let you change your spells, but players are encouraged to have the new spells pre-written.
Elemental subtypes: Why don't creatures of the plant type have [Nature] type instead of [Life]? Also, summoned elementals are not treated as outsiders for purposes of banishing, they are [Extraplanar].
Nature only applies to inanimate biomatter objects. Nothing does 'nature damage,' since nature is not actually an energy type. As for the extraplanar thing, that must've been one of the 3.5 changes I glossed over. I'll take a look at that; is it a big deal?
Friendly Elements: Is the energy resistance granted a total of 5 points in a round against the element and friendly elements, or 5 points each. Also, why do you go on your way to make energy resistance work the way it worked in 3.0 if this is supposed to update EoM to 3.5? Lastly, the second paragraph on this subject ends prematurely.
Huh. That's another 3.5 change I missed. In 3.0 it was a per-round resistance. Well then, I'll fix that.
As for the second paragraph ending prematurely, that's addressed above. It was an error in snipping.
Opposed Elements: This is, essentially, the Vulnerability to Energy special quality of the core rules, why is it not referenced as such?
Just a different choice of terminology. I didn't think to use that term, but I'll include it in the final version.
General enhancements, duration (concentration): Is there no limit to how long a mage can keep concentrating? This could result in very high-duration effects in a pinch (need to ride that dire wolf for a day and don't have enough MP to increase duration? Charm Animal with a concentration duration and couple of Concentration skill checks and you're dandy).
Can the Weather enhancement of Create Air be used if you have a duration of concentration? The letter of the rules say no, but the spirit would seem to be a working concenpt.
Of course, the problem is that, if you get distracted while concentrating, you've got a Dire Wolf trying to eat you. If you want to devote all your attention to a single spell so that it has a long duration, you're welcome to it. It could be broken if you hire a bunch of weenie wizards to cast Infuse spells on you to boost your abilities, then just concentrate for an entire day while you go off hacking at monsters, but generally I don't see it as a problem. As for the Weather enhancement, I'll change it so it says the weather takes 10 minutes to manifest, so if the spell ends early, you're out of luck. Concentrating will be viable.
Abjure Nature AC bonus: +11 Deflection bonus for 1 minute for the BBEG fight? Sign me in. Make that a +15 bonus if you know the BBEG's alignment! Why does the bonus get so high when in the core rules you can't get a Deflection bonus higher than +5 before getting into epic equipment?
This is an effect of how the system is different from the core rules. Now, Abjure Nature is supposed to provide an enhancement bonus to AC, whereas Force and everything else provides a deflection bonus, with force being even less than Nature. I see that's one of the things missing. (p.s., collaborative book-writing can get confusing sometimes)
In this system, there are still only a few sources of AC-boosting. Abjure is the primary one, Infuse Air for Dexterity increases also works, and finally you could use Transform to turn yourself into some nasty creature with high AC.
It's all a sort of rock-paper-scissors proposition. If you cast a spell that provides super high AC, then you haven't provided any protection from spells. If you know you're about to fight the Tarrasque, feel free to toss on +11 AC to defend against it, but usually you'd have something that grants some AC, some save bonuses, and some energy resistance. And mind you, these are 20-MP spells we're talking about. 20th level characters regularly do things that seem ridiculously powerful, but since both sides are doing it, it balances out.
In the field of magic items, it's possible to have +10 Full Plate with +10 deflection (total AC is +28), for the reasonable price of 801,650gp. That sort of stuff works fine for epic level games, but the more fighter common equipment we ended up defaulting to in our playtests is +6 Full Plate for 50,650gp, +5 deflection item for 49,000gp, a +5 saves item for 25,000gp, an energy resistance 10 (everything) item for 25,000gp, a +5 keen ghost touch weapon of some sort that does +2d6 force damage for ~100,000gp, two items for +6 Dex and Con for 72,000gp, one +10 Str item for 144,000gp, and then incidental other items. When you have that, sure, the mage can shell out 20 MP to give you a +5 AC bonus for one minute (since the bonus doesn't stack, it just replaces what the armor grants).
Create Element, Elemental Object: What kind of proficiency is it to use a weapon made from elemental force, the standard for a weapon it 'looks' like? The same with damage. Also, Elemental Object enhancement mentions that it does damage, but the Elemental Weapon says "...or you can choose it in addition to the elemental object enhancement, above, to create a weapon of pure damaging energy". Shouldn't that be "...to create a more damaging weapon of energy"?
An elemental object is just like a normal object of that type, except niftier looking, and if you hit someone with a fire longsword, it does 1d8 points of fire damage instead of 1d8 points of normal damage.
The wording is a little off there. For an example, if you create an elemental flame longsword that has the 2 MP elemental damage enhancement (a 4 MP spell), it'd do 1d8+2d6+Str points of fire damage per hit.
Create Element, Enduring Object (Life): So I need this to magically create a peg leg?
Well, I was thinking more along the lines of food. A pegleg isn't actually part of the creature. It's just an item.
Create Nature: Can this be used to create corpses (they were once living)?
It can, yes, but more commony it'll create wooden objects, things made of shell, etc.
Evoke Death, Infect enhancement: So I can infect mummy rot with this?
I don't know of any spell that causes mummy rot. It's not a disease; it's a curse. So no.
Evoke Death, Negative Level enhancement: Why can the target only lose a single level even if it has gained 5 negative levels from a single spell while in core rules (if my memory serves) you make a save for each level separately?
Oh, that's a typo. You still save for each negative level.
Evoke Fire, Elemental side effects: Should the damage done to an item by its own burning ignore hardness and the normal halving rule that is in effect with objects?
I'm not quite sure what you're asking here.
Evoke Nature, elemental side effects: "The damage is considered magical for the purposes of overcoming DR." Wouldn't this sound better as "The damage penetrates DR as if it was a magic weapon"?
The text doesn't say that you can choose which damage type (piercing, slashing or bludgeoning) the damage does, but implies that by saying that Evoke Earth only does bludgeoning damage. As the caster meant to be able to choose which type of damage to deal?
I'll use the 'magic weapon' statement.
Evoke Nature does just damage, nonelemental and nonspecific of slashing/piercing/bludgeoning.
Heal, Cure Affliction enhancement: Maybe change the end to "...heal afflictions with the same cost that Evoke Death causes them"? It took me a while to realise that's what it meant.
It's spelled out in the full text. I trimmed for space in the teaser.
Illusion, enhancements: While there are no skill checks to smell something, could the bonus not be applied to the Wisdom check that creature with Scent make?
I'll look into it.
Infuse with Element, Enhance Ability Score: Why does the Enhancement bonus to an ability score go up to +14? The greatsword wielding, Power Attacking barbarian is going to like this. Just Power Attack the gained to-hit bonus away for a total bonus of +24 (1,5*7+2*7) to damage per swing.
There are more efficient ways to kill things with magic than to buff a warrior buddy. The power attacking barbarian
should like this, if that's the way you want to use your spells.
Infuse with Force, Enhance Attack: +10 Enhancement bonus to all heads of that 12-headed hydra or that Colossal dragon? Ouch.
Indeed. Have you read the 'I killed the lich queen of the Githyanki in one round' thread? If you manage to have a giant reptilian ally or try to summon and charm one, then buff it, enjoy it. That's the kind of crazy stuff high level characters do.
Move Force: What is the effective size for performing special maneouvers with this spell?
Oh, I did forget to include that. It's Medium.
Transform Creature, Stronger Creature enhancement: Why does this not simply use the Swarm rules from the revised MM instead of allowing possible abuse of turning into a group of selves to cast a lot of spells in a round?
If you turn into several creatures, one keeps your mind; the others are just creatures. So you could have one 10th level wizard human and a bunch of commoner humans. There is a high-level option that lets you duplicate a low-level version of yourself, but that's complicated, so I won't get into it here.
