It sounds like a small little Pokemon is saying 'wee' over and over. And out of seemingly nowhere a little well groomed Eevee with hat, scarf, and vest on wanders into the cavern.

Brighteyes squeaks out a greeting for Lux and Ezreal, and twitches his left ear. There's a note tucked into the ear hole of his little knit cap.

Dear Ezzy and Lux,

It is rude to leave a girl waiting.

- Imogen Moreno, Delver.

P.S. I made a friend.

Brighteyes is standing right at the opening of the near invisible little cave Imogen had wandered down. His partner is off who knows where, but she was getting a bit bored waiting.