I control an Ambush Commander and the Essence of the Wild, then I play a Forest. Will it be a copy of the Essence of the Wild?

It will enter as a 1/1 Forest. That's due to this rule:

614.12. Some replacement effects modify how a permanent enters the battlefield. (See rules 614.1c–d.) Such effects may come from the permanent itself if they affect only that permanent (as opposed to a general subset of permanents that includes it). They may also come from other sources. To determine which replacement effects apply and how they apply, check the characteristics of the permanent as it would exist on the battlefield, taking into account replacement effects that have already modified how it enters the battlefield (see rule 616.1), continuous effects generated by the resolution of spells or abilities that changed the permanent’s characteristics on the stack (see rule 400.7a), and continuous effects from the permanent’s own static abilities, but ignoring continuous effects from any other source that would affect it.

The Essence has a replacement effect, so it's applied here. But the Commander does not: it has a continuous effect that would affect it once it's on the battlefield, but due to the last sentence, we ignore it. So the Forest will enter as a 1/1 Forest, not as a copy of the Essence.

Nathan Long
Wizards.Com Boards NetRep

Edited Nathan Long (Feb. 11, 2015 10:16:58 AM)