To know which side is face up, its simply the side with its mana cost but theres also an extra icon that can help too
Deck-building efficiency: Acquire playsets of common and uncommon cards for multiple deck strategies
Since it sacrifices, you get past protection like indestructible and since you didn't target, hexproof for protection won't help either
They often stick around longer than creatures or artifacts , so theyre good for ongoing effects
Immediate impact defines his role, but timing determines success
And thats not all: remove flying counters from your creatures placed on them by Luminous Broodmoth, slow down the aging of Cumulative upkeep cards, like Mystic Remora (or Blizzard, if you feel like putting flying counters on opponents creatures like a monster), allow Undying creatures to continually un-die the (giant robotic manta in the) skys the limit