The contract could even be that it has to be within the power of the other signatory to do.
It's not like Zaros could ask Zamorak to bring him the universe or a world or a star into the palm of his hand to fullfill his contract.
Zaros could phrase it that he meant it literally, not figuratively (so he can't do something like give Zaros a telescope).
Or dictating that Zamorak make Zaros an Elder God. What's Zamorak going to do, verbally annoint Zaros an "elder god", much the same way we call a kebbit a kebbit, or even naming a pet? Zamorak likely lacks the power, let along the knowledge, to elevate Zaros to that tier.
So by picking an impossible task, or at least functionally something that neither of them know is possible (let along probable) the contract might be voided.
Now situations like "Fight Armadyl/Saradomin to the death" would be possible.
Zamorak could conceivably fight either, and even win. And phrased in such a way that it didn't matter if Zam or Arma/Sara, or even both fighters died, it would uphold Zam's end of the deal.
21-Nov-2016 22:16:18