Our fellow fans over at
The Allspark have translated the final two chapters of the Transformers United EX story that came with Assault Master and Build Master. The identities of these last two characters are not left up to interpretation - Assault Master's story chapter, Hope for the New Generation, outright states that Assault Master was meant to be a spare body for
Optimus Prime himself, but ends up being piloted by the human,
Clouder - a character from Masterforce better known as the double-dealing
Doubleclouder. Build Master's name is outright given in his bio as
Gravedigger, a Constructicon introduced in a Find-your-fate book called "Dinobots Strike Back".
The story chapters end on a bit of a ambiguous cliffhanger note, with the final fate of the characters in particular Clouder, who comes face to face with the Decepticon High Regent Scrash (a villain alluded to in Operation Combination's phone-in stories in Japan in 1992). There's also a very cool allusion in the Unearthed Future story chapter, implying that relics from the Beast Wars - namely, the lair of Tarantulas - is being unearthed in the United EX time period by the Decepticons of Master Chaos.
Although the story ends on a cliffhanger, the Allspark reports that the story may continue down the line in some form in other media. Here is hoping that such a story comes to pass, especially after an ending like that!
Click here to check out the full story translation.