The stealth cloak is a consumable accessory that makes you invisible to mobs and turrets for 20 seconds. Stealth cloaks don't hide you from other players: while in effect, your character will appear semi-transparent and your name will still appear over your head.
Raising your Agility Skill level increases stealth cloak duration.
Stealth cloaks are located in the Accessories section of your inventory.
How to Obtain
Stealth cloaks drop as loot from chests, crates, barrels, and sacks. You can also trade for them in a market world or purchase them directly from the in-game crowns store.
How to Use
If you're using an iOS device, swipe up the gear located at the bottom-right of your screen and tap the cloak icon. It makes you invisible for a short period of time: brains and turrets won't sense your presence, so you can sneak through a dungeon without much trouble.
If you're using a keyboard device, you can hit F to bring up the power-ups and then click on a cloak from there.
Also, on any device, you can put the stealth cloaks in your hotbar, select, and then click anywhere on screen to activate.
Stealth cloaks were added in December 2012 as part of the 1.3.11 release.