Activate Agonasaur Rex's cycling ability by paying 2 and discarding it.
Agonasaur Rex triggers, putting two +1/+1 counters on Evolution Witness.
Evolution Witness triggers, returning Agonasaur Rex from your graveyard to your hand.
Kheru Goldkeeper triggers, creating four Treasure tokens.
Resolve the Agonasaur Rex ability from step 1, causing you to draw a card.
Activate three Treasures by tapping and sacrificing them, adding 2.
Repeat.
This ingenious loop turns a simple cycling trigger into an engine for infinite resources. By discarding Agonasaur Rex to its own cycling cost, you trigger its ability to place +1/+1 counters on Evolution Witness, which in turn lets you recur the Agonasaur right back to your hand. Meanwhile, Kheru Goldkeeper exploits cards leaving your graveyard by generating Treasure tokens, which are then doubled into an abundant surplus thanks to the replacement effects of both Mondrak, Glory Dominus and Bard, King of Dale. Sacrificing just a few of these doubled Treasures provides all the green mana needed to pay for Agonasaur Rex's cycling cost again, while the excess card draw from the cycle natively feeds Bard, King of Dale's second ability to keep your hand fully stocked.