Usually, the Shift keyword enables players to place a more powerful version of a character on top of another card - matching the requirements - for a cheaper ink cost than paying the full ink price for the character, as well as immediately putting that character into a readied state
Cast something, Greven is deadlier
Cateran Slaver Cateran Slaver is part of the mercenary tribe from Mercadian Masques and has the typical tribal ability that lets it tutor up another mercenary card with lesser mana cost
You can run it in blue decks in order to add in burn and mass removal
These, like other Universes Beyond cards, are legal in Legacy, Vintage, and EDH only
Sword of Forge and Frontier Land and card draw The Swords of series in Magic: The Gathering run a gamut of usefulness, but all of them cost three mana, grant protection from two colours, add +2/+2 and provide some kind of benefit if you can hit a player with a creature equipped with them