This human cleric rewards you with both mana and cards (the two most important resources in Magic) for sacrificing creatures (what your deck was going to do anyway)
Still, if you don't already have the rare duals, replacing them with Contaminated Aquifer and Dismal Backwater is a fine plan for the short term, although in the long term, you'll probably need to upgrade to compete at the higher ranks
Krabby Fossil Symbol Error: Certain Krabby cards from the Unlimited print run were printed with an incomplete Fossil set symbol
During the End Phase, if this card destroyed a monster by battle this turn: You can send this face-up card to the Graveyard
A: Not directly, but reputable stores like Card Brawlers ensure authentic, untampered products
While it only affects the creature type you name, it provides cards when those creatures ETB or attack