You wanna know what should be added into the game, or at least considered? A boss resembling Cerberus. I feel as if, no matter how you decide to approach making it a boss, the fight agents a three headed dog would be AMAZING. It should be fightable somewhere in hell after beating Plantera and it could drop some cool new weapons. I pitch this idea, for there seems like a lacking number of things to do after beating Plantera and before beating Golem. After beating the Wall of Flesh a few times, there's almost no reason to ever return to hell so, it would also shine some light on hell again. I'd imagine the den it would be summoned in would resemble a glorified bee hive containing a tomb to dig up oppose to a larva to break.