Hm, recently there is a lot of speculation around about Tarn’s identity (Roller or the original Ultra Magnus e.g).
I have to admit, I can not not speculate myself. ;)
Even if I prefer the “Tarn = a bot we are not familiar with” resolution (a genuine new character) - so let his mask on, Mr. Roberts! - I have my own thoughts about this particular mech.
I see the strongest link/hint to Tarn’s past so far in this scene:
"I’d forgotten how much I hate you.”
Call me crazy - I can see: Tarn is Skar.
Yep, yep the buddy is supposed to be dead and that all but Skar has a reason to hate Grimlock with a passion (even if one can say that Skar with his dynamic alt-mode adaption started the ball rolling) and he has a deep connection with the process of transformation itself (said adaption).
Oh and there are those scars (sic) on Tarn’s face … ;P
Maybe Megatron “stumbled” upon the left for dead Skar and saved him; I think Tarn’s devotion and loyalty to Megatron must have a strong base, why not a life debt …
Just my two cents.