Hippos are a small creature type with limited direct typal support, best known through Phelddagrif and its long association with political and Group Hug decks. Dedicated Hippo decks are therefore usually built as much for theme as they are for mechanical efficiency.
Phelddagrif can hand opponents life, creatures, or cards in exchange for its own advantages, while cards such as Mirror Entity and Maskwood Nexus can help fill out a Hippo army when the natural herd runs thin.
