It does give that player a bunch of 1/1 Elf tokens, but that likely wont affect you too much
All of the Merlin cards give an ability when returned to hand, like the Merlin Crab which gives another character +3 strength when challenging, when they are played, and when they leave play (which can be in the same turn for a super boost), and Madam Min returns cards to hand when played
Cards will never rotate out, which means fans can play any card in their collection, regardless of the set it came from
At the beginning of your end step, if you control four or more artifacts, return target creature card from your graveyard to your hand
Completing the Quest there earns you a Violet Parr Learning New Powers Seasonal Promo card
This legend isnt that strong outside of some cool synergies, though