Multiattack. Sarlok makes two Firebolt attacks.
Firebolt (Cantrip): Ranged attack, 2d10 fire damage
Magic Missile (1st Level): Auto-hit, 3 missiles dealing 1d4+1 each
Mirror Image (2nd Level): Creates illusory duplicates of himself
Quickened Spell (Sorcery Points). Hanya can spend 2 sorcery points to cast a spell as a bonus action instead of an action.
The newly forged Zetsubou stone is ripping the cave a apart, every 2 turns, earthquakes wreck the battle field, and parts of it will fall into the abyss
An outcropping that looks over the fires of Mt Fuji's volcano
will stay at a distance, using Mirror Image to avoid hits while sending Magic Missiles and Scorching Rays at the party. If pressed, he will cast Hold Person on the strongest fighter and retreat behind his minions. Once the lackeys are disposed, if he is the last one, he will cast fireball in a desperate last attack