Interloper

Interlopers are warlocks who have experienced so much trauma that their brains fold in on themselves, dissociating with reality to the point where they form a new one based off their fragmented mind, usually these realities are small pocket dimensions, where the interloper can conjure spells that are placed into the real world. When placing said spells into the real world however, they take some damage depending on the spell's damage.

mental fortitude

You lose a specific amount of hp for using a spell rather than using a spell slot.

For each spell class(cantrip, 1st, etc), theres a set amount of health lost, the only exception being if a spell takes away a specific amount of health/other form of stat(max health, stat modifiers, etc)

Cantrip: 1d4
1st level: 1d6
2nd level: 2d6
3rd level: 3d6
4th level: 1d8
5th level: 2d8
6th level: 1d10
7th level: 2d10
8th level: 3d12
9th level: 4d12

You also have resistance to necrotic and psyphic damage.

Mind Arena

As an action, you can transport yourself and 3 other people into the pocket dimension where your spells come from. This pocket dimension typically is the size of a large room, kinda like a gym or a ballroom or..something. The look and layout of the room can be manipulated however you want oit of combat besides the actual size. Whilst in your arena, you have advantage on all your attack/spell rolls, +1 to all your ability modifiers, +3 to spell prof./attack, and of you rolled a 10 or lower, you can reroll it once.

This lasts until 10 of your turns have passed during conflict, and can be ended at any time before that...obviously.

soul seeing

Every 10 turns, you can force up to 7 people to look into your memories, making them roll an intelligence saving throw with disadvantage. If the roll fails, they take 2d12 damage and are paralyised for 3 turns. 

If the person has something that shields their mind, then they dont roll with disadvantage nor do they take any damage.

The Ungod's Power

Starting at 10th level, you have finally seen into the voids and found something, you call it The Ungod. The Ungod bestows you an ability to see into the traumatic memories of others and amplify their effect on their mind, turning them so insane that their mind shuts down for 6 turns, allowing you to temporarily command them to do things.

Calcified mental state

When you cast spells, damage you take from it subtracts by 10 + your constitution modifier, only exception are spells that can kill you instantly, also you regain 5 hp every 2 turns and 50 after a short/long rest. You also gain a bonus action that doubles your walking speed, strength modifier, and adds +2 to your initiative, and the ability to swing whatever weapon your using extremely fast, allowing your attacks per action to increase 2 times more(lowest being 2, highest being 8). This lasts for 2 turns, and can't be used again unless you take damage at full health.