darc kills zipher by trapping him wounded in a specifc area, here he also reveals his token powers and takes zipher to the past and travels to the present to find ziphers body as a skeleton

when we learn darc is actually a token as zipher does

darc chases zipher out into the surface world and eventually corners him in a specific trappable room (or darc traps him in place somehow)

when darc is about to travel back to the present zipher lunges at him but doesnt make it in time, darc arrives at the present and looks down to see ziphers skeleton

zipher has no rott powers on the surface

zipher doesnt actually die and instead joins the blood runners giving them humanoid parts

he puts a blood runner skeleton in the place of his body that darc put him

maybe we get to see his venture and perhaps he unites with truman

darc makes his own decision to kill zipher

zipher doesnt attempt use his powers against darc in metrodome instead the entire fight/chase sequence is darc using his token powers