Echo is a delayed payment. When a permanent with echo enters the battlefield under your control, it stays for now. At the beginning of your next upkeep, if it came under your control since the beginning of your last upkeep, its echo ability triggers. You may pay the echo cost shown in its reminder text; if you don't, you sacrifice it. In practice, the card asks for little mana up front but demands more on your next turn.
That trade-off shapes how the card plays. You get an undercosted body immediately, which can block, attack, or provide an effect before the bill arrives. Later you decide whether the board state still justifies paying. If the permanent has already left the battlefield, the echo trigger won't force that choice. It rewards planning your mana and knowing when to let a temporary threat go.
