HK-T4 has had every external component painted black as night, with attempts to minimize the brightness of external lights and features. This allows this HK-model Gladiator Droid to more easily blend into the shadows and darkness unseen.

HK-T4 has been modified from standard design parameters to be fitted with reinforced plating. As a result, when compared side by side with the standard HK-model Gladiator Droid, HK-T4 is found to be more durable while its ability to move has been inhibited.

HK-T4 has developed a predatory nature similar to those often associated with assassin droids. As a result, HK-T4 will often approach a situation with the mind set of a hunter, and convey their findings as such. This can be disconcerting to others who are unaccustomed to HK-T4.

HK-T4 has had its programs re-written and mechanical systems hard-wired for combat operations. This augmentation gives this HK-model Gladiator Droid a significant increase in combat efficiency in eliminating targets on behalf of Astronicus "Tron" Aurelius Sadow, but at the expense of it being usable for much else except for combat.