Goblin Patrol

The deal echo offers is brutally simple: one red mana now buys a 2/1, then a second red is due the turn after or the creature is gone. That math makes this less a threat than a budgeting problem, because the timing punishes you precisely where the rate looks generous. Echo collects at the beginning of your upkeep, which arrives before combat. With no haste, this can't attack the turn it lands, so the first event of the turn it could finally swing is the echo trigger demanding payment. Decline, and it dies before it ever connects: there is no free hit in the sequence, paid or unpaid. Attaching a one-time delayed tax to an above-rate body was an early-era way of pushing aggressive creatures into the format, and this is that discipline applied at the cheapest point on the curve. A 2/1 for a single red is a forward-loaded bargain only because the back end is real, but the toll is collected once; from that upkeep onward it swings as an ordinary 2/1. The friction is that the cost lands on your own clock rather than the opponent's, and on the exact turn you most want to be deploying threats. You either spend the second red to keep a vanilla 2/1 breathing, or you watch your first mana evaporate having purchased nothing. Weighing that single deferred toll is the whole exercise echo was built to impose.