Daoin of Naiil (Star of Naiil)

Summons a crystal bomb which detonates in 1d4 turns or instead, by command of the caster, either as a bonus action or a reaction to the movement of an enemy. At detonation, the crystal deals 3d8 force damage to everyone within 5ft. Additionally, everyone within 15ft of the blast must make a Dexterity saving throw or take 3d4 piercing damage. 
However: With AC 7, these crystal can also combust on being hit for damage greater than 2xSpell Level AND the crystal cannot be detonated on the same turn of casting.

At higher levels. The damage increases by 1d8 force and 1d4 piercing for every slot above 2nd level. 
3rd level, 1d8 & 1d4; 4th level, 2d8 & 1d4; 5th, 3d8 & 3d4; . . .