This guy isn't very tough at all if you're maxed out, have some Super Monster Milks, some Bubble Shields and Super Pike Balls. Got all that? Then yeah boss is cake.
So his random spawns are a tad frustrating. The dude is gonna teleport around like Dracula from Castlevania. He will eventually summon bone pillars and stand on top of them firing projectiles. If you have a bubble shield equipped and you don't want to risk any unnecessary damage just chill and wait for him to go back into his Dracula Teleport phase. By then you should have put in enough damage to end his first phase.
If you collected all of the Dark Magic (20 Cacklebats) his true form will be the next fight.