Players highly value most dual land cards, but Underground Sea is one of the most difficult to get your hands on because of its high price tag
If you gain control of a spell with Commandeer for which buyback has been paid, the card returns to its owner's hand
Probably not forever, but two-mana to exile anything is just such phenomenal value
Ravenous Creatures The ravenous creatures, mostly associated with Warhammer 40,000 , are X-spell creatures that cantrip when they enter if X=5 or greater
Then if youre the monarch, this enchantment deals X damage to each opponent, where X is the number of creatures you control
Once activated, this legendary artifact lets a player control another's turn, and the only caveat is that Mindslaver's controller cannot make the other player formally concede the game