Theft is a very important ability late in the game. It is the only way to get the best items, and it is an easy way to get good items in the endgame.
To steal, you have to use one of the 'Hand' items (Stealing Hand, Plunder Hand, Cha-Ching Hand, Bandit's Hand, Awesome Hand, Dream Hand). Simply go to 'Item' on the character action menu, select the hand you want to use, and move the cursor to the character you want to steal from. (Note: if you fail, you do not lose the hand.)
Rogues are much better at stealing than other classes, though any class can steal. Their levels count double in the formula, they have twice the maximum chance to steal, and they can steal opponents' stats as well as items.
Rogues have a chance to steal items and stats governed by the following formula:
c = h + t*2 + 25 - e - r*3 - a
|c||The percentage chance to steal.|
|h||The HIT statistic of the hand being used (including specialists).|
|t||The level of the thief.|
|e||The level of the enemy.|
|r||The rank of the item.|
|a||0 if the rarity of the item is Normal, 10 if the rarity is Rare, 30 if the rarity is Legendary, or 100 if the item has rarity 0.|
Statistics are considered Normal rank 0 items for this equation.
A Rogue can have, at most, a 99% chance to steal.
Other classes have a chance to steal items governed by the following formula:
c = h + t - 30 - e - r*3 - a
Non-Rogues cannot steal statistics and have, at most, a 50% chance to steal. Note that Thursday is an exception to this rule. Thursday can steal stats but follows the formula for non-rogues.