lapis saffron
Surface: Tier 4 maybe?
Surface would be a stand bound to an armor stand. Why do we need this one time appearance stand? Well, it would be kind of interesting to see a stand bound to an item or entity so yeah!
Surface's 1st ability is to mimic any mob or player that is the nearest to it. If Surface is mimicing a mob, it will have that mob's AI (slightly altered to not try to attack you and have none of the original mob's abilities like teleportation for Endermen) and will visually change it's appearance to the mob except for a nail on it's forehead area. If Surface is mimicing a player, it will have similar AI to a tamed dog. However, the stand can be remote controlled rather than having the usual AI of the mob/player. Surface will follow you around kind of like a tamed mob. Surface during the mimicry will have the same hitpoints as the armor stand it was bound to. The shift variant is for Surface to turn back into an armor stand.
Surface's 2nd ability is forced synchronization. For it to work, you have to be within range of the mob/player you mimiced (Around 5 blocks maybe?). During this, the mob/player affected by this ability is forced to mimic the stand. This ability is mainly best used for remote control mode and would be pretty useful. How it would work is that if Surface faces in a direction, The mob or player will have to mirror the same action.
For Surface's attacks... Good question! I think that maybe the stand wouldn't necessarily have attacks and more of be able to hold items (for certain mobs and players).
Surface's 3rd ability could be to bound itself to a new armor stand. If the armor stand has any equipment on it, the equipment will stay on during Surface's mimicry.