If you'd like help slotting these generators into a Commander deck, Karn can help identify the best options for your colors and commander
Along with the Theros Temples, Pathways are the cheapest way to fix your mana, as theyre only being used in some Pioneer decks

Ancient Hydra Apex Devastator Apocalypse Hydra Balduvian Hydra Benevolent Hydra Bioessence Hydra Briar Hydra Bristling Hydra Capricopian Clockwork Hydra Domesticated Hydra Feral Hydra Gargos, Vicious Watcher Genesis Hydra Goldvein Hydra Grakmaw, Skyclave Ravager Gyrus, Waker of Corpses Heroes' Bane Honored Hydra Hooded Hydra Hungering Hydra Hydra Broodmaster Hydra Omnivore Hydradoodle Hydroid Krasis Ironscale Hydra Kalonian Hydra Khalni Hydra Lifeblood Hydra Managorger Hydra Mistcutter Hydra Molten Hydra Mossborn Hydra Multi-Headed Nessian Wilds Ravager Neverwinter Hydra Nyxborn Hydra Oran-Rief Hydra Phyrexian Hydra Phytohydra Polukranos Reborn Polukranos, Engine of Ruin Polukranos, Unchained Polukranos, World Eater Primordial Hydra Progenitus Protean Hydra Rampaging Aetherhood Rampant Rejuvenator Ramunap Hydra Rock Hydra Savageborn Hydra Scourge of Skola Vale Shivan Devastator Spitting Hydra Sprouting Phytohydra Steelbane Hydra Steelbane Hydra Stumpsquall Hydra The Goose Mother Thunderous Snapper Ulasht, the Hate Seed Ulvenwald Hydra Vastwood Hydra Voracious Hydra Voracious Hydra Warden of the Grove Whiptongue Hydra Wildwood Scourge Wren's Run Hydra Zaxara, the Exemplary

This first flavor of chaotic-commander warps game mechanics into rule-bending pretzels
Prince Eric is (potentially) a two character banishing card capable of taking out lower cost characters with his two strength (or finishing off weakened ones or locations)
Some decks like Temur Rhinos play Force of Negation in the maindeck, but most opt to play it in the Sideboard and bring it in when it shines