Pinkymod/Artillery Tortoise

The Artillery Tortoise is a Hardmode found in the Underground Jungle. It walks towards the player while firing missiles at them from its mortar, the player will be able to tell when the tortoise is about to fire as the mortar will begin to aim at them.

Bestiary Entry
Horrifying creature that once was, at some point of its life, a Giant Tortoise. New, the only organic matter left is its brains and veins, encased in a shell of Chlorophyte. On its back is a mortar, made to fight back against all attackers. Also, its shell is replaced for a see-through container to store its ammunition. If you are lucky, you might even get it to drop its mortar undamaged if you land your blows just right.

Knowing that the Lihzahrds and Hornets probably made these up, I am quite surprised to see that they didn't stick a thousand flamethrowers in it blasting 'Profaned Flame' or whatever dumb magic fire it is those lizardmen worship.