Can't remember the card name, or even what kind of card it is (I THINK it's a Spell). What I do remember is that it allows you to tribute a monster you control in order to special summon one with exactly the same number of stars from your Fusion deck. I used to use it a lot around the time the fusion deck got limited to 15 cards, but it has been a long time. Trying to get back into the game and would like to re-make my old deck first, as conforming to current ban/restrict lists.
Found it , the card was metamorphosis