Enchantment Echoes of Eternity If a triggered ability of a colorless spell you control or another colorless permanent you control triggers, that ability triggers an additional time
Its a common, but it certainly gets the job done
But its ability lets you play an extra land and then draw a card to repeat the process if you still have lands in your hand
While other cards over the years have featured effects similar to this (mythic rare Zur, Eternal Schemer from Dominaria United comes to mind), Opalescence was the first to do it en masse for enchantments, and, due to its novelty and being first on the scene, it clocks in with a price point approaching $30
Its an effective commander, though, and my personal zombie legend of choice
In fact, I would say that there are some situations where you should be playing these cards