Terraria's early bosses break into Hallownest, using the real sprites, sounds and boss music read from your own Terraria install.
How it plays
Six Terraria summoning items are hidden around Hallownest: the Slime Crown in Dirtmouth, the Suspicious Looking Eye and Bloody Spine in the Forgotten Crossroads, Abeman's Larva in Greenpath, Worm Food at Queen's Station and the Clothier Voodoo Doll in the City of Tears.
Press T (or click the right stick) to use the item you're holding and summon its boss right where you stand. Press G (or the left stick) to switch items.
Fight with everything the Knight has. Nail hits give SOUL, you can pogo off the bosses, and spells work too.
King Slime hops, belly-flops, teleports and sheds slimes.
Eye of Cthulhu calls Servants, dashes, then tears open its mouth.
Eater of Worlds tunnels straight through the walls and spits.
Brain of Cthulhu hides behind Creepers, then blinks around you with illusions.
Queen Bee charges, sprays stingers and calls bees.
Skeletron claws with both hands, spins and fires cursed skulls.
Bosses scale with your progress (nail upgrades and masks), so you can take them on in any order.
Each boss drops its Treasure Bag: Geo plus a Terraria accessory you wear like a charm (up to three at once, in Options › Mods › Bosses from Below): Royal Gel, Shield of Cthulhu, Worm Scarf, Brain of Confusion, Hive Pack and Bone Glove.
If you leave the room or fall, the boss leaves and you get the summoning item back.
Needs Hollow Knight (1.5) and Terraria (1.4.5) installed. Single player. Nothing from Terraria is included: the mod reads it from your copy every time you play.