When triggered, duplicates of each character appear and begin attacking their counterparts. The doubles will only attack their likenesses, and will not help their fellow duplicates. The doubles have the exact same statistics, powers, and items as the characters they have copied at the moment that the trap is activated, and will use these things to fight in the same way as the originals. This includes spells, and any previous unhealed damage accrued. The doubles and their copied items all disappear the moment that either they, or their corresponding originals, die. Optional: Should the original characters be able to retreat or evade the duplicates without killing them, the duplicates will remain in existence, and try to hunt the originals down no matter where they go.
man covering his face standing by Alex Iby. Modified by David in Inkscape. Unsplash License.