Crucible of the Spirit Dragon
Land
{T}: Add {C}.
{1}, {T}: Put a storage counter on ~this~.
{T}, Remove X storage counters from ~this~: Add X mana in any combination of colors. Spend this mana only to cast Dragon spells or activate abilities of Dragons.
Selvala, Heart of the Wilds
{1}{G}{G}
Legendary Creature -- Elf Scout
2/3
Whenever another creature enters, its controller may draw a card if its power is greater than each other creature's power.
{G}, {T}: Add X mana in any combination of colors, where X is the greatest power among creatures you control.