Interesting! I'm going to see if I can offer some helpful comments on each part.
Turning EB into a class feature is something I've seen mentioned often when it comes to warlock changes. It prevents other classes from getting Eldritch Blast via Magic Initiate or Spell Sniper, and it lets warlocks pick an extra cantrip. A perhaps unexpected change is that EB no longer works with Spell Sniper, so no more sniping from 600 feet away. Likewise, anything that interacts with spells no longer effects EB.
I'm confused as to why you'd want to nerf EB, though? 1d10 at 120 feet was fine before. Since it's no longer a cantrip, it doesn't have to compete with other cantrips such as Fire Bolt. I could understand the nerf if it was to make it more competitive with other cantrips, but that's no longer an issue. Why not just leave it as-is?
You should probably also make sure to specify that EB is, indeed, magic, since it is no longer a cantrip. Using a spell attack, as you've mentioned, is probably sufficient. Alternatively, you could leave it as a cantrip and simply give it to every warlock for free.
Something you might consider is rolling the EB and pact boon invocations into the base class. For example, as you level, you can occasionally choose an EB enhancement, and automatically get all your pact-specific invocations as regular class features. Of course, this is quite the power spike, so it might need to come at the expense of something else. Maybe a simple option would be that as you level you get two extra invocations that can only be spent on EB invocations, and one invocation that can only be spent on a pact invocation. It would be logical for these to come at levels 6, 10, and 14.
This seems like something that should perhaps be unique to Blade pact warlocks. Also, does this cost anything to do?When you make a Weapon Attack, you can choose enhance that weapon with your Patron's power, using your Eldritch Blast's damage type for that attack.
Overall, I like what you've done here. I do wonder a bit about this making magic weapons less useful to bladelocks, since they can no longer make them pact weapons. What I might do is allow them to touch one magic weapon to add that to their list of possible enhancement choices. Doing so makes the magic weapon disappear until either you die or you touch a different magic weapon to make an enhancement choice. You can only do this with one magic weapon at a time.Pact of the Blade
You might also consider giving them a +1 and +2 bonus at certain warlock levels, as if the weapon was now a weapon +1 or +2.
So if I'm surrounded, I get a +8 to AC? Why is this here, where did it come from?
- Gain a +1 AC bonus for each adjacent enemy.
This is pretty cool. What's the bonus? Perhaps equal to the spell slot level? That might be too strong, actually.You can instead choose to expend a Spell Slot to conjure your Pact Weapon without an Action or to enhance a weapon you’re already wielding. Doing so grants you a bonus to your AC and to attacks you make with a weapon enhanced by Eldritch Power, equal to the level of the Spell Slot spent, until the start of your next turn.
The whole warpcast thing is interesting. Not sure how I feel about it yet. It's also not clear if you still get the three cantrips or not.Pact of the Tome
What about something like this? If you add 1 minute to the casting time of a spell (i.e. "if you're not in combat"), you can cast the spell without expending a spell slot.
Alternatively, bake Book of Ancient Secrets into the base pact boon, and change the invocation to add one spell for each level up to 5th to your ritual book, even if it doesn't have the ritual tag.
I like this. It really lets you get full use out of your familiar. I might restrict the "casting through someone else" to just the familiar, but leaving it open-ended like this allows for more potential use-cases.Pact of the Chain
One thing I'm wondering about is, if charmed creatures have disadvantage on saves to resist being cast through, and willing creatures won't resist and therefore don't need to save, then who makes the save regularly, without disadvantage? No one?
One thing I'm wondering is if EB still does force damage, and these other damage types are just alternatives. If so, then it should be fine. If not, and these are the only damage type you have for EB, then some changes need to be made. Fire, and especially poison, are some of the most commonly resisted damage types. I would change the Tormented patron to use magical piercing damage instead of poison. I might let Fiend patrons have both fire and cold; neither is a great damage type, but being able to choose either gives you some versatility.Patron Modifications:
I don't actually have enough experience with either of these to leave a comment on them yet.Hexblade Patron
Renamed to the Tormented Patron.
[...]
Undying Patron
You've inspired me to look into creating an elemental patron, like a djinni or something. Seems like a missing gap in the list of possible patrons.