Ivy the Poisonous Mass

Leaps at a target up to twenty tiles away and slams down in a five by three tile box, knocking players back, smashing every wall within three and a half tiles while it is in the air, and covering the ground where it lands in slime.

Mortar shot: hits for 80 damage, 14 times per use, up to 15 tiles away, every 10 to 20 seconds.

It puts these on the ground:

Poison Slime Boss Mortar Projectile

Hops around near where it spawned when nobody is in range, waiting ten seconds between hops and never straying more than twenty five tiles from its spawn point.

Enrage starts when its health falls to 30 percent.