Tiamat domain

you have been chosen as a slave to Tiamat from Tiamat for her vengeance if your party finds out you will die if you are in a place scrying sensors can be

bonus immunity

When you choose this domain at 1st level, you gain immunity to damage from cantrips

Disciple of chaos

Also starting at 1st level, your damaging spells are more effective. Whenever you use a spell of 1st level or higher to lower hit points to a creature, the creature becomes stunned

Channel Divinity: summon chaos

Starting at 2nd level, you can use your Channel Divinity make a creature turn the tides of battle

As an action, you present your holy symbol and evoke chaos energy that can cause chaos  Choose 1 creature within 30 feet of you they must attack their ally's if they can for one minute you cannot target creature that is not hostile to you unless it is a enemy to Tiamat

Tiamat's blessing

Beginning at 6th level, the damaging spells you cast on others heal you as well. When you cast a spell of 1st level or higher that damages hit points to a creature other than you, you regain hit points equal to the spell’s level.

Divine Strike

At 8th level, you gain the ability to infuse your weapon strikes with divine energy. Once on each of your turns when you hit a creature with a weapon attack, you can cause the attack to deal an extra 1d8 necrotic damage to the target. When you reach 14th level, the extra damage increases to 2d8.

Supreme damage

Starting at 17th level, when you would normally roll one or more dice to damage hit points with a spell, you instead use the highest number possible for each die. For example, instead of restoring 2d6 hit points to a creature, you restore 12.