Echoes of Eternity rewards colorless decks twice: it adds another trigger to qualifying colorless spell and permanent abilities, and it copies each colorless spell you cast. A copied permanent spell becomes a token when it resolves, so an ordinary artifact or creature can become two permanents from one cast. The original card's relevant cast triggers may also receive an additional trigger.
Kozilek, Butcher of Truth illustrates the different layers. Its cast-based draw ability can trigger an additional time from Echoes. The copied creature spell is not cast, so creating that copy does not generate another new cast trigger of its own. Legendary copies also face the legend rule unless another effect changes it, meaning the extra permanent is not always a lasting second threat.
Nonlegendary artifacts and creatures offer simpler duplication. A Wurmcoil Engine copy can remain alongside the original, and both can benefit from the additional qualifying death triggers while Echoes remains present. Mana rocks and utility artifacts can likewise become a larger resource base.
The casting cost contains three actual colorless mana symbols. Colored mana cannot normally pay those requirements, so the mana base needs sources that produce colorless, not merely enough total mana. Echoes also excludes its own colorless-permanent trigger from its first ability, preventing it from automatically doubling its spell-copy trigger through that wording.
This is a six-mana setup card with a high ceiling. Cast it when the deck can follow with useful colorless spells soon, and distinguish extra triggers, spell copies, and new casts when planning a complicated turn. They interact, but they are not interchangeable events.
