Unique to a Zaxara Hydra deck is the inclusion of Villainous Wealth, a sorcery that allows you to exile and cast X spells from the top of another player's library
Perfect for a legendary creature-focused deck, Jodah, the Unifier is capable of providing some truly insane buffs
Under $10: Cryptbreaker, Zombie Master (if you're adding Urborg, Tomb of Yawgmoth), Balthor the Defiled, Crypt Ghast, Graveborn Muse, Grimgrin, Corpse-Born, Living Death, Dimir Signet, Beseech the Queen Pricey stuff: Sidisi, Undead Vizier, Relentless Dead, Lord of the Undead, The Scarab God, Mikaeus, the Unhallowed, Phyrexian Altar, Yawgmoth's Will, Vampiric Tutor, Demonic Tutor, Intuition, Cyclonic Rift, Tombstone Stairwell, dual lands, fetches, you know the stuff If you want to enhance your finisher potential even further, then adding Phyrexian Altar makes your Gravecrawler combos much more powerful, but that's a $70 investment
Requiring players to manage both aggression and disruption, Tempo tests a lot of the key skills in MTG arguably further than even Control