Fiend Hunter

The two triggers are written to read as a clean pair, but the gap between them is the entire game. "Exile when it enters, return when it leaves" looks like tidy bookkeeping until you notice nothing forces those events to resolve in order, and a generation of players learned to slip a sacrifice or bounce effect into the window before the enter-the-battlefield trigger ever resolves. Respond to the first trigger by removing the body, and the exiled creature simply never comes back: the leaves-the-battlefield trigger fires first and finds nothing in exile to return. That stack-order quirk turned a defensive 1/3 into a permanent-removal engine and a sacrifice-fodder staple, the kind of unintended depth that flash-removal "oops, all gone" tricks have rewarded ever since. The fix Wizards eventually landed on (Banisher Priest folding both effects into a single duration, then Banishing Light moving the same idea onto an enchantment) still holds the creature hostage; what changed was tying exile and return to one continuous effect, so killing the jailer no longer strands the prisoner in exile. This design is the one that taught them the difference matters. As written, it is a hostage exchange rather than a removal spell: kill the Cleric and the prisoner walks free, attack into it and you trade a card for a stalled board, but the moment you can make the jailer disappear without giving back the key, the trade becomes a steal.