Unstable Protolich

Spell Expulsion. The Unstable Protolich has a pool of spell slots with one slot corresponding to each level up to 8th. Each slot can be expended to cast any spell of that level or lower. It is recommended that the DM prepare a list of two spells of each level for the Unstable Protolich to cast. These spell slots are directly related to the Protolich's ability to hold its form. So, with the expulsion of the last spell slot. the Unstable Protolich rapidly released the magical energy stored in its body causing a each creature within 30ft of it to make a dexterity saving throw or take 10 d10 force damage on a fail or half on a success from the resulting explosion. This causes the Unstable Protolich's body and soul to be completely destroyed.

Negligible Spellcasting.  The Unstable Protolich can cast any cantrip as if they were a 15th level spell caster.

The Unstable Protolich can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The lich regains spent legendary actions at the start of its turn.

Spell Surge. The Unstable Protolich casts a spell using a spell slot. This spell can only have a casting time of an action or bonus action

Arcane Shield (Costs 2 Actions). The Unstable Protolich taps into its arcane reserves to negate all effects until its next turn effect. The Unstable Protolich uses a spell slot of at least 3rd level to automatically succeed on all saving throws until the beginning of its next turn.