Neo Genesis is the first set for which I believe there are such artificial rarity differences for valuable cards
Reanimator strategies traditionally focus on placing high converted mana cost (CMC) creatures in your graveyard, then use low CMC cards (usually 3 or less, almost never more than 5 CMC) to revive them onto the battlefield
On top of that, Hammer of Nazahn gives the creature it's attached to indestructible and can also be equipped as it enters the battlefield, immediately protecting any creature you want from being destroyed
Grade them for the $, then remove if they get any heat
In Ravnicas wilder districts, nature still stirs, and its protectors still mind their posts
Ratchet, Field Medic Ratchet, Field Medic is not on this list because it's the scariest Lifelink card ever printed