Nightstalker is the catlike partner of Ravage.
Marvel Comics UK continuity
Nightstalker, along with his partner Ravage, was the bodyguard to the last surviving Overlord, an enfeebled old Autobot who needed constant re-energizing to stay alive (think 24/7 life support). When the Overlord visited the city-state of Tarn, war broke out between it and its neigbor, Vos, forcing the Overlord to retreat back to his own home in Iacon. Accompanied by Optimus Prime and a then-non Decepticon Megatron, the Overlord almost made it, but was tracked down and cornered at the bridge to Iacon by Tarn's forces, who had blown it out before they got there. Nightstalker, in a display of extreme loyalty to his charge, detonated a self-destruct mechanism installed in all the Overlord's bodyguards as a last resort, taking out all of Tarn's forces with him.
He shouldn't have bothered; the Overlord died soon afterwards from energon deficiency after Ravage betrayed him and sided with Megatron, refusing to give up his own energy to sustain the old, rusting fool.
Nightstalker may have been loosely based on a similarly-named fan character that was entered into (and won) one of Marvel UK's character creation contests. This character, named "Night Stalker" (with a space), was less of a Ravage clone in design, with a canine robot mode (though with a similar color scheme to that of the Decepticon feline).