The epic event is one you should try hard to play both copies every game. 5 direct damage, movement for the summoner, and +1 Strength for a turn. Huge value if you can use it properly.
The catch? Nimid must be adjacent to deal the 5 damage, which isn’t easy. The most reliable combo is with Seed Bearer: move an enemy next to Nimid during the movement phase, then Unroot, then reposition Nimidi.
That said, don’t be afraid to use it early just to reposition Nimid, its placement can determine the game’s flow.
In the late game, Unroot becomes terrifying. Eldiri can move adjacent, deal 5 damage, then attack, 9 total damage. Even champions can be one shotted.