Ashnod's Transmogrant [Fifth Edition] Hippo War Falcon can't attack unless

War Falcon can't attack unless you control a Knight or a Soldier

Set: Eighth Edition Type: Creature — Human Soldier Rarity: Uncommon Cost: {4}{W} Vigilance

Set: Commander 2013 Type: Artifact Creature — Phyrexian Construct Rarity: Uncommon Cost: {4} At the beginning of each opponent's upkeep

Set: Urza's Saga Type: Creature — Elemental Rarity: Rare Cost: {3}{G}{G}{G} Trample

You can only use this effect of "Arisen Gaia the Fierce Knight" once per turn

Ashnod's Transmogrant [Fifth Edition] Hippo War Falcon can't attack unlessSet: Fifth Edition Type: Artifact Rarity: Common Cost: {1} {T}, Sacrifice Ashnod's Transmogrant: Put a +1 +1 counter on target nonartifact creature. That creature becomes an artifact in addition to its other types. Ashnod found few willing to trade their humanity for the power she offered.