Nafaalilargus, Loyal Vassal

Flying, Trample, Thuum
Subordinate — At the beginning of combat on
your turn, if you control an emperor creature,
create a colorless gold artifact token with
"Sacrifice this artifact: Add one mana of any
color to your mana pool."
I am Tiber Septim's proud Soldier, loyal Vassal,
a jewel of the crown.