Gargantua is a red-skinned Jägergeneral sporting a beard and long blondish mane. It is possible that "Gargantua" is a disparaging given to him by a hostile Wulfenbach soldier, rather than his real name.
One of his commentsthat he might be among the younger members of the Jäger leaders. (Youth of course being a relative term in this case)
His rather spiffy outfit ("Vot? Dis old ting?"), while exposing rather too much skin to be fairly called "armor", does come equipped with large organic-looking spikes or horns which he can rip off andas projectile weapons. Or possibly the spikes are part of his body and poke through holes in his shoulder-guards. If so, ouch.
He and the other generals assist Tarvek in saving the surviving members of the crashed Vespiary Squad from the attacking Wulfenbach forces. He takes part in the betting as to whether Agatha will ultimately choose Tarvek or Gil as a mate, going with "both".