Mana-Harvester Dragonling

Hexproof, defender
{t} Add {b} or {r} to your mana pool.
{1}{t} Mana-Harvester Dragonling gets +0/+1.
When Mana-Harvester Dragonling has 7 or more
toughness, sacrifice it. When you do, create a 5/9
red black Mana-Harvester Dragon with
hexproof, vigilant, and "{t} Add {b/r}{b/r}{b/r} to your
mana pool."