Open them at the crates at spawn. Every crate lets you pick your reward, no spinning.
Pick 1 of 7 enchanted diamond pieces.
Pick 1 of 7: better diamond gear or a netherite ingot.
One piece of this season's emerald set. Five keys gets all of it.
Pick 1 of 10 maxed netherite tools and weapons.
3x3 drills, OP shovels, chopper or sell axe, haste. Lasts 24 hours.