Zardnaar
Legend
I am not a fan of the blade [ppact warlock as I think it has many of the same problems most of the other gish classes in the PHB have. The bladelock however carries it to extremes.
1. It is not proficient with constitution saves which nmakes maintaining concentration spells difficult for a front line combatant. This almost defeats the purpose of playing a arcane gish PC.
2. Without the warcaster feat it can be difficult to even cast spells anyway although this may not be a problem for the bladelock since it cant use a shield anyway
3. It is not proficient with any armor that matters only light. Kind of heavily implies you should be dex based and using a rapier with an empty off hand. This means low AC as well or you pile all your stat buffs into dexterity. And then your AC will still be low as you do not have a shield.
4. Multiple ability dependency. You probably want decent strenght or dex along with charisma. Then you want a decent con score as well but your AC will be terrible and you only have a d8 hit dice. Even if you can where medium armor you now want a decent con, dex, cha, and str score. A few of these issues can go away if you roll dice instead of the default stat array.
I played a Valor [bard to level 14 and kind of cocked the PC up as it dealt very little damage in melee and it cast spells fine but then why did I not just play a lore bard to begin with? After learning from this I discussed the problems I thought most gish classes in the game have (points 1-4) and came up with this solution.
Take a single level of fighter 1st and MC into the bladelock (or valor bard etc). This gains you.
1. Proficiency in con saves.
2. Proficiency in shields and heavy armor.
3. a weapon style which can help with low damage/AC depending on what you like.
4. 2nd wind as a bonus action. 1s10+1 will not be that great for long but its a freebie on top of all the other goodies.
5. Solves the MAD issue and low AC as you can wear heavy armor and just have a decent str/cha score and a moderate con score. Even with he default array you can have 16/14/14 as a human or 16/16/14 as a half elf. You AC will now be in the 18-20 range before magic or weapon styles are factored in.
I would argue the fighter dip level (starting as a level 1 fighter) solves all the problems the bladelock has (and gish PCs in general).
So my idea is a Fighter1/WarlockXYZ as the base class. This means you can now concentrate reliably on hex for starters. If you like sword and board I would probably look at the shield master feat and great weapons the great weapon master or sentinel feat. The shove part of the shield master feat has some cute interactions with the hex spell which provides disadvantage on skill checks (athletics for example). You do not need warcaster as much as you are proficient in con saves. For most of your career until level 8+ you will likely only need to cast 2 spells on yourself probably outside of combat. Those spells are.
1. Armor of Agthys.
2. Hex.
Hex is an out right damage buff spell. Armor of agathys looks crap but starts becoming decent using higher level spell slots and that is what the warlock excels at. At 4th level you get an extra 10 hit points per short rest, 15 at level 6, 20 at level 8. This helps relieve the burden on the healers in the party and also deals more damage to NPCs who hit you. The spell also gets cute with low damage NPCs and damage mitigation abilities to make armour of Agathys even better. Once you can make hex last for 8 or 24 hours on subsequent short rests you in effect gain an extra spell slot to use per short rest. Note AoA doesn't require concentration.
For invocations the only required one as such is thirsting blade which you can pick up at level 5 or 6 depending on how your DM rules the required level part. RAW you can be 5th level but some DMs may require 5 warlock levels. Thirsting blade also offers charisma to damage at level 12 or 13. Our bladelock also took agonizing blast for versatility. Unlike most strength based fighters you will not suck at range. Your basic damage will be weapon+str+cha+1d6+ whatever damage you get out of Armor of Agathys.
Now the otherworldy patrons thing. I think you could make any of them work but the prize seems to be the fiend. This is because of the Dark Ones blessing which grants temporary hit points of your charisma modifier+ warlock level. Not this is when you reduce an opponent to 0 hp and range doesn't matter. This means eldritch blast is even better. It is not hard to have a shield of temporary hit points available especially once Armor of Agathys runs out of juice.
What spells the patrons offer mostly doesn't matter as you probably will not be casting them anyway. A high level archfey bladelock using greater invisibility + the sentinel feat could be funny. Still the fiend seems to be the best offering for the bladelock as the other abilities at warlock level 1 do not matter as much for a bladelock.
1. It is not proficient with constitution saves which nmakes maintaining concentration spells difficult for a front line combatant. This almost defeats the purpose of playing a arcane gish PC.
2. Without the warcaster feat it can be difficult to even cast spells anyway although this may not be a problem for the bladelock since it cant use a shield anyway
3. It is not proficient with any armor that matters only light. Kind of heavily implies you should be dex based and using a rapier with an empty off hand. This means low AC as well or you pile all your stat buffs into dexterity. And then your AC will still be low as you do not have a shield.
4. Multiple ability dependency. You probably want decent strenght or dex along with charisma. Then you want a decent con score as well but your AC will be terrible and you only have a d8 hit dice. Even if you can where medium armor you now want a decent con, dex, cha, and str score. A few of these issues can go away if you roll dice instead of the default stat array.
I played a Valor [bard to level 14 and kind of cocked the PC up as it dealt very little damage in melee and it cast spells fine but then why did I not just play a lore bard to begin with? After learning from this I discussed the problems I thought most gish classes in the game have (points 1-4) and came up with this solution.
Take a single level of fighter 1st and MC into the bladelock (or valor bard etc). This gains you.
1. Proficiency in con saves.
2. Proficiency in shields and heavy armor.
3. a weapon style which can help with low damage/AC depending on what you like.
4. 2nd wind as a bonus action. 1s10+1 will not be that great for long but its a freebie on top of all the other goodies.
5. Solves the MAD issue and low AC as you can wear heavy armor and just have a decent str/cha score and a moderate con score. Even with he default array you can have 16/14/14 as a human or 16/16/14 as a half elf. You AC will now be in the 18-20 range before magic or weapon styles are factored in.
I would argue the fighter dip level (starting as a level 1 fighter) solves all the problems the bladelock has (and gish PCs in general).
So my idea is a Fighter1/WarlockXYZ as the base class. This means you can now concentrate reliably on hex for starters. If you like sword and board I would probably look at the shield master feat and great weapons the great weapon master or sentinel feat. The shove part of the shield master feat has some cute interactions with the hex spell which provides disadvantage on skill checks (athletics for example). You do not need warcaster as much as you are proficient in con saves. For most of your career until level 8+ you will likely only need to cast 2 spells on yourself probably outside of combat. Those spells are.
1. Armor of Agthys.
2. Hex.
Hex is an out right damage buff spell. Armor of agathys looks crap but starts becoming decent using higher level spell slots and that is what the warlock excels at. At 4th level you get an extra 10 hit points per short rest, 15 at level 6, 20 at level 8. This helps relieve the burden on the healers in the party and also deals more damage to NPCs who hit you. The spell also gets cute with low damage NPCs and damage mitigation abilities to make armour of Agathys even better. Once you can make hex last for 8 or 24 hours on subsequent short rests you in effect gain an extra spell slot to use per short rest. Note AoA doesn't require concentration.
For invocations the only required one as such is thirsting blade which you can pick up at level 5 or 6 depending on how your DM rules the required level part. RAW you can be 5th level but some DMs may require 5 warlock levels. Thirsting blade also offers charisma to damage at level 12 or 13. Our bladelock also took agonizing blast for versatility. Unlike most strength based fighters you will not suck at range. Your basic damage will be weapon+str+cha+1d6+ whatever damage you get out of Armor of Agathys.
Now the otherworldy patrons thing. I think you could make any of them work but the prize seems to be the fiend. This is because of the Dark Ones blessing which grants temporary hit points of your charisma modifier+ warlock level. Not this is when you reduce an opponent to 0 hp and range doesn't matter. This means eldritch blast is even better. It is not hard to have a shield of temporary hit points available especially once Armor of Agathys runs out of juice.
What spells the patrons offer mostly doesn't matter as you probably will not be casting them anyway. A high level archfey bladelock using greater invisibility + the sentinel feat could be funny. Still the fiend seems to be the best offering for the bladelock as the other abilities at warlock level 1 do not matter as much for a bladelock.