Ancient Copper Dragon without summoning sickness and cannot be blocked by an opponent).
Steps
Deal combat damage to an opponent using
Ancient Copper Dragon, triggering it, causing you to roll a d20 and create that many Treasure tokens.
Move to your postcombat main phase.
Activate a Treasure by tapping and sacrificing it, adding ({R} magic symbol) .
Repeat step 3 until you have ({3} magic symbol) ({R} magic symbol) ({R} magic symbol) or run out of Treasures.
Activate
Aggravated Assault by paying ({3} magic symbol) ({R} magic symbol) ({R} magic symbol) , causing you to untap all creatures you control and to get an additional combat and main phase after this one.
Repeat.
Notes
This combo can fail if you roll less than a 5 and do not control enough Treasures to make up the difference. You can control creatures that tap for mana and/or have additional mana to start the combo and reduce the chance of failure. You can also carry over Treasures from prior iterations to cover the difference.
Results
Near-infinite colored mana.
Near-infinite combat damage.
Near-infinite Treasure tokens.
Near-infinite combat phases.
Near-infinite untap of creatures you control.
Near-infinite mana creatures you control can produce.