Thriving Ibex

If a spell or ability with one or more targets states that you "may pay" some amount of energy , and each permanent that it targets has become an illegal target, the spell or ability won't resolve. You can't pay any energy even if you want to.

If an effect says you get one or more energy , you get that many energy counters. To pay one or more energy , you lose that many energy counters. You can't pay more energy counters than you have. Any effects that interact with counters a player gets, has, or loses can interact with energy counters.

Some triggered abilities that state that you "may pay" a certain amount of energy describe an effect that happens "If you do." In that case, no player may take actions to try to stop the ability's effect after you make your choice. If the payment is followed by the phrase "When you do," then you'll choose any targets for that reflexive triggered ability and put it on the stack before players can take actions.