A Dance With Dragons

You may spend mana as if it were mana of any color
to cast this spell.
When A Dance With Dragons enters the battlefield,
each player creates a 6/6 red dragon creature token
with flying and "{3}{t}:Deal 4 damage to any target"
and a 5/6 green dragon creature token with flying
and "{4}{t}: Destroy target artifact."
Dragons must attack each combat if able to do so.
When only one player controls a dragon creature,
that player sits the Iron Throne. Sacrifice A Dance
With Dragons.