According to the game rules, the creature is treated as a new object when it re-enters, and the original target no longer exists
They're a resource that you can use to pay costs, like the ones offered by cards such as T-45 Power Armor
The criteria for our ranking of the sets are pretty basic: we're considering how good the cards in each set are from both a competitive standpoint (i.e
A galaxy foil rare (2%) or mythic rare (1%) borderless viewport land A textless singularity foil Sothera, the Supervoid appears in less than 1% of Collector Boosters 1 Art card or traditional foil double-sided token A traditional foil double-sided token appears in 65% of Collector Boosters
If you chain this effect to a quick play spell or trap card (which would destroy themselves once they resolve anyway) then you can special summon a free monster at no cost whatsoever
Beyond those, however, the Mentor cycle of cards exemplifies this concept fairly well