The card is very powerful, but I think not too powerful given the wide array of premium threats printed in recent years
How Is a Tribal Instant Different from a Regular Instant
(9/19/2025) If any permanent has an ability that triggers when the permanent you return leaves the battlefield, that ability will be put on the stack after you finish casting the spell, and it will resolve before that spell
(Plus Merlin, Shapeshifter in his own human form.) Each of the shapeshifting Merlin cards offers a different boon when they first arrive on the table and when they leave, presenting the opportunity to combine them with cards that cycle them in and out of your hand to stack up the benefits
Grenzo, Dungeon Warden Unfortunately for Grenzo, Dungeon Warden, it has a much better alternate version
In fact, if an effect is super splashy, we most often move it to mythic rare