The epic event of Valeria and extremely versatile, it will be hard to not find a use and thus generally worth keeping in hand whenever drawn. The list of uses is extensive but being able to reposition units on the attack phase is a proven potent effect in Summoner Wars and this is just a great iteration of it.
The most powerful use is the most obvious one: take the best common of the opponent and bring it next to Valeria for the team to decimate the poor soul.