Aspect of Might is a Defensive Aspect that can be found by completing the Dark Ravine Dungeon as well as from random enemy drops. After clearing Dark Ravine for the first time the Aspect will be available in your Codex of Power.
How to Obtain - Codex of Power - Dark Ravine
Aspect of Might Mechanics
Legendary Aspects can change the way skills and builds work in significant ways.
For further information, see our Build Guides, Legendary Aspects & Codex of Power
Aspect of Might