The Zeta Burst is a truly terrifying attack guaranteeing a massive amount of damage but at great cost. 

Received from a powerful god, it is stored in a scroll that can be used Twice. 

Must be at least level 7 to use, and the enemy must be substantially powerful for this spell to activate (D.M must rule on this). When activated one enemy, within the user's sight, loses 70 or 75% of their HP.  This is a guaranteed hit and has no save. (unless the D.M. chooses to add one.) In exchange the user will permanently lose access to 2 of their current highest level spell slots. If used a second time they lose access to 1 spell slot. Spell slot can only be restored using Wish. 

A side effect of using this causes a tattoo of the god's symbol to appear in halfs on the users hand.