Rezo has to mull their words over, which is a laborious process given his current state of overwhelm. On a purely physical level he'd much rather just keep burrowing into the creature's paws and let its purring drown out any thoughts, but both survival instincts and logical reasoning tell him it would be unwise to ignore a god.

If they don't know him, why go to the effort of reviving him? He fears this may have something to do with his connection to Lord Ruby Eye, but even as he thinks this he realizes...

He can't feel Lord Ruby Eye. Where once there had been a red presence, now he has a sense of emptiness.

Rezo slams the brakes on any attempt to even begin processing whatever feelings he has on that. An odd feeling doesn't prove anything. The Dark Lord can be a very subtle thing. He has survived being fragmented, sealed inside a soul for five thousand years, and being eviscerated with the raw power of the Sea of Chaos herself. Certainly, Lord Ruby Eye is more durable than Rezo, and Rezo's the one here and alive and-!

And he should probably address the reason for his being here.

"...What service do you require of me?" His tone is very careful, neither resentful nor fawning.