Trample, haste (This creature can deal excess combat damage to the player or planeswalker it's attacking. This creature can attack and as soon as it comes under your control.)
At the beginning of the end step, sacrifice Spark Elemental.
Trample, haste (If this creature would deal enough combat damage to its blockers to destroy them, you may have it deal the rest of its damage to defending player. This creature can attack and as soon as it comes under your control.)
At end of turn, sacrifice Spark Elemental.
Vulshok shamans could never keep them alive for more than a few seconds, yet those few seconds seemed to be enough.