Green mana doesn't empty from your mana pool as steps and phases end. Omnath, Locus of Mana gets +1/+1 for each green mana in your mana pool.

• Number: 7
• Rarity: P
• Power: 1
• Toughness: 1
• Type: Legendary Creature
• Subtype: Elemental
• Mana cost: 2G
• Color: Green
• Artist: Mike Bierek