Returning the Elf you control to its owner's hand is the cost to activate the ability
While there are solid cards like Cut Your Losses for Bruvac mill or Hypnotic Grifter as a mana outlet in a self-mill deck, theyre a little niche and otherwise not going to add too much to your collection
Both also afford great synergy with all things top of library based such as miracles, Courser of kruphix, Devler of Secrets, Domri Rade etc
In trial games against decks that exile graveyards, creatures that have already been destroyed could be tactically cleverly played to protect them
You might be able to stave off destruction by truthfully promising that Full Throttle is the only extra combat spell in your deck
Like, until The Tenth Doctor put three time counters on As Foretold I really could not care that he was present at all until he did that