Crypt GhastCrypt Ghast, DeathgreeterDeathgreeter, ExsanguinateExsanguinate, Gray Merchant of AsphodelGray Merchant of Asphodel, and Vampiric LinkVampiric Link provide enough of a buffer to keep you jumping along (notably, Vampiric Link gains you life even if an opponent controls Kain)
Id play this in decks where you can create a 4/4 or 6/6 land consistently
Pairing it with something like Marauding Raptor allows you to create an infinite amount of Polyraptor clones

higher rarities will start to mix and match effects): Artifact destruction Artifact or enchantment destruction (Naturalize) "Bounce" (Returning nonland permanents to owner's hand) Card drawing Card filtering Creature destruction Creature lockdown (Pacifism and Dehydration) Creature regrowing (Raise Dead) Creature unblockability Counterspell Damage prevention (Fog) Direct damage Discard Draining creatures and/or players Enchantment destruction Fighting "Flickering" (exile and return a creature to the battlefield) Flier destruction Forced blocking Forced sacrifice "Impulsive draw" (exile a card or cards, can cast until end of turn) Land fetching Life gain Looting/rummaging (drawing and discarding, and vice versa) "Milling" (putting cards from top of library into graveyard) "Panic" (some number of creatures can't block) Power/toughness pumping (Giant Growth) Tapping creatures (including "freezing" them, where they don't untap) Temporary stealing (Threaten) Token making Uncommon Complexity Uncommon gets to raise the bar a little on comprehension complexity and a bit more on board complexity

Sealed Booster Box contains 30 packs
This is an odd card to evaluate, as it doesnt affect the board but also offers a pretty powerful life swing