×The serpent is too quick. At best, I was 5 moves from the orb when the doors were triggered.

×1. The shortest length an adder can reduce itself to is 3, if it is the only one.
2. Rattlers must be killed, as Adders can't kill them.
3. The rattlers are trapping the adders, so killing the rattlers is stop and go (well, more so than usual...).
4. And I must kill all rattlers and adders with enough time to make it to the orb before the serpent reaches the door at turn 154.

×shortening the west rattlesnake three tiles, then killing the long adder completely.