This is the most commonly used damage Legendary Gem, increasing your damage by 15% multiplicatively against enemies under the effect of control-impairing effects. You can level this Gem all the way up to rank 150. Every upgrade will increase the damage gain by 0.3% up to a maximum of 60% total. Control-impairing effects are: Fear, Stun, Freeze, Chill, Knockback, Immobilize and Slow including the Rank 25 effect of this Gem, making it proc itself in a 15 yard radius.
Bane of the Trapped Best Use
The DPS Gem: Used in basically every damage dealing build. This is one of the most powerful and commonly used Gems in the game! Ranged Cold-based builds like the Frozen Orb Wizard have an easy time proccing this Gem as many Cold skills momentary apply Chill. In Group gameplay this Gem is usually proc’d by the supports with skills like Furious Charge, Crippling Wave Tsunami or Multishot Wind Chill.
Legendary Gem in Diablo 3
Legendary Gem Creation:
If you need extra Legendary Gems to level up, you can make the Rift Guardian in any Greater Rift drop a new Rank 0 Gem by removing all the Legendary Gems with the same name from your Equipment, Inventory and Stash.
The safest way to do that is to put them into the Inventory of different character.