Gain 2% additive damage for 1.5 seconds when you spend resources with a channeling skill. This effect stacks up to 10 times. You can level this Gem all the way up to rank 150. Every upgrade will increase the additive damage by another 0.04% per stack up to a maximum of 8% total. Furthermore the rank 25 bonus increases your Armor by 2% for each stack. At max rank and stacks this Gem provides a whopping 80% additive damage increase as well as a 20% Armor buff.
Taeguk Best Use
Very strong for channeling builds: This Gem grants offensive and defensive buffs alike and is used by almost every build that relies on channeling Skills like the WW Rend Barbarian or the PoJ Tempest Rush Monk. In groups however, its damage value is generally significantly decreased as this gem grants additive damage and supports already bring quite a lot of additive damage buffs to the party.
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.