Flying
At the beginning of the end step, if you control no Goblins, sacrifice Stenchskipper.
This ability checks whether you control any Goblins twice each turn: once when the ability would trigger, and once when it resolves. If you control any Goblins at either time, you won’t sacrifice Stenchskipper. (If you control any Goblins at the time the ability would trigger, it doesn’t trigger at all.)