({1} magic symbol) ({R} magic symbol) ({W} magic symbol) ({B} magic symbol) plus enough mana to pay for commander tax, if applicable, or an additional ({R} magic symbol) , ({W} magic symbol) or ({B} magic symbol) if you haven't cast Jirina from the command zone this game available.
Steps
Cast Jirina from the command zone by paying ({1} magic symbol) ({R} magic symbol) ({W} magic symbol) ({B} magic symbol) plus commander tax, if applicable.
When Jirina enters the battlefield, it and Mana Echoes trigger.
Resolve the Jirina trigger, creating a 1/1 Human Soldier creature token for each time you've cast Jirina from the command zone this game.
When the Human Soldiers enter the battlefield, Mana Echoes triggers that many times.
Resolve the first Mana Echoes trigger, adding ({C} magic symbol) for each Human and Soldier you control.
Repeat step 5 for each remaining Mana Echoes trigger created in steps 2 and 4.
Activate Altar of Dementia twice by sacrificing Jirina and a Human Soldier.
Choose to return Jirina to the command zone from your graveyard.
When Jirina and the Human Soldier die, Pitiless Plunderer triggers twice, creating two Treasure tokens.
Holding priority, if you control a Human Soldier, activate Altar of Dementia by sacrificing a Human Soldier.
If you sacrificed a Human Soldier this way, Pitiless Plunderer triggers, creating a Treasure token.
Resolve the Altar of Dementia abilities from steps 7 and 10, causing target player to mill cards equal to the sacrificed creatures' combined power.
Activate up to three Treasures by tapping and sacrificing them, adding any combination of ({R} magic symbol) , ({W} magic symbol) and ({B} magic symbol) .