Pretender

From Transformers2005 MUSH Wiki

In G1 canon, Pretenders are Transformers that have a sort of shell that goes around their form, granting them additional abilities or weapons. The robot inside is entirely hidden within the shell, though can emerge at will. The word Pretender can refer to either the shell itself or any Transformer that has one.

At 2k5, a Pretender TP was run in which Thunderwing and some of his cronies created Pretender shells that any Transformer could use. These powerful enhancements were eventually gained by both the Autobots and Decepticons, but were revealed to be part of a grander scheme by Thunderwing. Eventually the shells were destroyed.