Amber Chaos Emerald

{t}: Add one mana of any color. Spend that mana
only to cast legendary spells.
{t}, Sacrifice Amber Chaos Emerald and 6
artifacts you control with the words "Chaos
Emerald" in their card names: Put 10 +1/+1
counters on target creature you control.
It gains hexproof, indestructible, and flying.
Those who gather all seven emeralds
are forever changed.