Do all units die if Singularity damage equals total Might on the battlefield?

You Singularity a 10-Might Mountain Drake on a battlefield, then move in a 5-Might unit and a 4-Might unit to start a Showdown. A player asked whether you win because the Drake dies, or whether everyone dies.

If Singularity leaves marked damage equal to units' total Might, do all units die in the ensuing combat?