The Infinity Key is a gamepass by Rukiryo, this enables users to always be able to open chests with keys.
"This key unlocks chests dropped by mobs. When a mob drops a [Normal Chest] this chest has a chance to give an item (chance depends on how rare the item is). If a mob drops a [Legendary Chest], you can buy a 15R$ key to unlock it, or use the Infinity Key(450R$) on as many chests as you want. This key will have paid itself off after you open 45 chests (I actually made this key really cheap...)"