Royal Gel

Type	Accessory
Tooltip	Slimes become friendly
Rarity
Sell	2
Research	1 required

Desktop/Console/Mobile-Only Content: This information applies only to the Desktop, Console, and Mobile versions of Terraria.

Expert Mode-Only Content: This information applies only to Expert Mode and Expert Mode worlds.

Royal Gel is an accessory obtained from the Treasure Bag dropped by King Slime in Expert Mode. While equipped, most slimes will become friendly, no longer pursuing the player, and will deal no contact damage or fire projectiles, even if the player deals damage to them.

This does not apply to the following slimes:

Hoppin' Jacks
King Slime and his Spiked Slimes, though the normal Blue Slimes that King Slime spawns remain docile.
Queen Slime and her Bouncy Slimes, Crystal Slimes, and Heavenly Slimes.

Notes

Minions and NPCs will continue to attack all nearby slimes.
Since Gastropods and Toxic Sludges are slimes, they are affected by the Royal Gel as well.

Tips

This accessory is particularly valuable during Slime Rain, as it allows the player to kill almost all enemies without worrying about taking damage.
This accessory can keep Lava Slimes away while building a bridge for the Wall of Flesh, especially useful since they spread lava on death. In Hardmode, they can prevent Gastropods from shooting the player with lasers, making it much easier to fish or farm enemies in The Hallow at night.
This accessory can be a very useful tool in the Underground Jungle early on, as it prevents Spiked Jungle Slimes from shooting their thorns at the player.

Trivia

The Royal Gel's name may be inspired by royal jelly, a food substance that bee workers feed to bee larvae to change how they grow, specifically so the larvae can become a queen bee.