Its an easy inclusion in ramp decks, or in decks that will cast their 5MV+ commander many times in the game
If you cast it without a Time Vault, you could go find it and threaten to take infinite turns, next turn
Putting the deck together requires you to determine how your mana will be able to cast spells and summon creatures, so limiting yourself to two or three colours is a good place to start
Dinner Bell wouldnt make most of my Sealed Decks either, as its only useful in the very late game
Essentially, if you have a full party with all four of these on the board, you can pay one white, one blue, and one black mana to give the Warrior lifelink, deathtouch, and make him unblockable (deathtouch and unblockable at the same time has no real use, but thats still OP to think about)
Cecil & Kain from Final Fantasy IV Much like his game counterpart, Cecil can transform from a Dark Knight to a Paladin under certain conditions