Thunder-Thrash Elder

You may choose not to sacrifice any creatures for the Devour ability.

If multiple creatures with devour are entering under your control at the same time, you may use each one's devour ability. A creature you already control can be devoured by only one of them, however. (In other words, you can't sacrifice the same creature to satisfy multiple devour abilities.) All creatures devoured this way are sacrificed at the same time.

If you cast this as a spell, you choose how many and which creatures to devour as part of the resolution of that spell. (It can't be countered at this point.) The same is true of a spell or ability that lets you put a creature with devour onto the battlefield.