Once invisible, the caster can run past enemies, and any enemy targeted to them will return to their starting position. In pvp, the opponent will lose their lock on the caster. While invisible, the caster is free to move, heal, attack, etc. However, in pvp, the opponent will be able to see the healing animation. The invisibility lasts until the caster dies, the buff wears out, or attacks. Fast Walker will not cause invisibility to wear off.