You don't lose unspent green mana as steps and phases end.
Omnath gets +1/+1 for each unspent green mana you have.
Ramp into massive mana production, then hold green mana across turns to grow Omnath into a lethal threat while keeping that pool available for instant-speed plays. You float green mana through end steps, swing with a huge Omnath, and use the banked mana to power X-spells, big bombs, or protection.
Huge mana acceleration in mono-green makes ramp consistent and explosive
Omnath becomes a free, scaling beater just by floating mana
Banked green mana enables instant-speed interaction and X-spells without tapping out
Mono-green is cheap, focused, and easy to tutor pieces with green's robust ramp suite
Omnath is fragile to removal and board wipes, losing all your floated-mana investment
Mono-green lacks card draw, instant-speed interaction, and counterspells
No native way to deal direct damage or punch through chump blockers without trample
Floating mana is wasted if you can't deploy it before drawing-out, and you must commit to Omnath as the engine
Legendary Creature — Elemental
