Sphinx of the Revelation

Some spells and abilities that give you {E} may require targets. If each target chosen is an illegal target as that spell or ability tries to resolve, it won't resolve. You won't get any {E}.

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

Each creature with lifelink dealing combat damage causes a separate life-gaining event. For example, if two creatures you control with lifelink deal combat damage at the same time, Sphinx of the Revelation's triggered ability will trigger twice. This may be relevant if you control a permanent with an ability that triggers "Whenever you get one or more {E}."

Some triggered abilities that state that you "may pay" a certain amount of {E} 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.

If an effect says you get one or more {E}, you get that many energy counters. To pay one or more {E}, 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.

{E} is the energy symbol. It represents one energy counter.