The Queen Slime is a Hardcore only boss in Terraria that can be found in the Hallow biome. It looks just like a giant slime, but is wearing a crown, and is a pinkish color. To find the Queen Slime, you will need to use a Gelatine Crystal.
Gelatine Crystals can be found in the Underground Hallow and can be broken and harvested the same as any other tile. Outside of the Hallow, the Gelatine Crystal has no use. To summon the Queen Slime, just use the Gelatine Crystal while you are in the Hallow. Remember to use it somewhere that gives you plenty of room to move.
The Queen Slime will quickly jump around the level, often directly at you, and will do damage if it hits you. It can also fire projectiles in different directions, but these will shatter against blocks, so you can protect yourself from them using cover. When reduced to half health, the Queen Slime will start to aim the crystals directly at you.
The Queen Slime will also grow wings, and attempt to crush you by flying over you and then falling straight down. The Queen Slime can drop the following items on death:
- Sparkle Slime Balloon (guaranteed)
- Queen Slime Mask
- Crystal Assassin’s Hood
- Crystal Assassin’s Shirt
- Crystal Assassin’s Pants
- Gelatinous Pillion
- Treasure Bag
- Regal Delicacy
- Queen Slime Trophy
- Queen Slime Relic
It goes without saying that you should be very careful before you summon the Queen Slime, as she can end your Hardcore game if you are unprepared.