The Kremlin (Opal Palace)

{t}: Add {1} to your mana pool.
{1}, {t}: Add one mana of any color in your
commander's color identity. If you spend this
mana to cast your commander, it enters the battlefield with a number of additional +1/+1 counters on it equal to the number of times it's
been cast from the command zone this game.
Onion roof.