You can think about it in decks like Teysa Karlov where you sacrifice creatures but also take advantage of tokens, like with the afterlife mechanic
Bloodlord of Vaasgoth Bloodlord of Vaasgoth makes all your other vampires fantastic threats
Then, suddenly, all your creatures have deathtouch and lifelink
Any time you have priority, you may turn a manifested creature face up by revealing that it's a creature card (ignoring any copy effects or type-changing effects that might be applying to it) and paying its mana cost
Combine that with art of Minnie in an adorable scuba suit, and you've got a league promo that's worth earning (if not buying)
Theyre intended for casual play, playtesting, house rules, cubes, and fun projects with your group