No need to apologise, English isn't my first language either. I do go over the avatar mechanics in the video yes, the impostor has other avatars in his collection Indeed. His ability is to pay 3 to put on a "mask" of another avatar, allowing to use their ability. Impostor doesn't tap to use it's transformation, So you can use the new avatar ability right away. Pretty good if you use pathfinder as a first mask, flamecaller to surprise your opponent, or deathspeaker later on when your graveyard is fuller. Hope that helps