Urborg Phantom

The blue activation is what marks this as an Invasion-block card and nothing else. The set was built around heavy multicolor commitment, and the design language ran the other way too: monocolored cards loaded with off-color activated abilities meant to reward splashing or full domain decks. A black Spirit that pays one blue mana to fog itself in combat is exactly that experiment, a 3/1 beater whose evasion of removal-by-blocking comes packaged with a defensive trick from across the color pie. The body itself reads aggressive: a 3/1 that cannot block is pure offense, the kind of statline that wants to be attacking every turn and trading favorably or not at all. The blue ability bends that, letting it swing into a larger blocker and walk away clean, or survive a combat-damage-based removal swing, provided you have the second color online. That dependency is the whole tension of the card: the power is real only when the mana is there, and the mana being there was the block's central ask. Read outside that context it looks like a fragile attacker with a niche button, which is roughly how it has aged.