Dr. Karos is one of the easiest bosses within the Vethea Dimension.
He is yellow with orange-tipped tentacles and has eyes that come out of his head.
Dr. Karos constantly rains exploding red balls (according to the code, they are Zoragon bombs) from the Heliotic Beams in the ceiling. He also shoots Karos Arrows from the Karos Cannons in the walls. It seems that he is the one spawning these projectiles inside the blocks (not the blocks), but in a future update, the blocks themselves may start shooting the projectiles. These projectiles aren't too strong.
Another thing to watch out for is his Karos Heat Tiles. When green, they are fine, but when red, they will rapidly damage and kill most things that touch it.
It's not too hard to dodge or endure these mechanisms, so Dr. Karos is quite easy.
He has 4000 health and will drop some Karos Lumps when killed (along with experience points).
"You can't kill me, you WEAK excuse for a human!"
"I am here for you, to make your doom!"
"Do you like explosives? Hahaha!"