The Sin War
Astrogha appears as a giant, humanoid spider. His lower body is that of a spider, but his torso and head resemble something vaguely human. On his head he has several hand-like limbs, used for pushing prey into his mouth. He also has many smaller spider-spawns made of his essence, called 'Children', who act as spies. Astrogha also has the ability to create thick webbing which he uses to constrict prey in. He feeds on human bodies, sucking out their fluids.
Astrogha is a somewhat reluctant ally of Lucion, though he always remains true to his lord, Diablo. Astrogha once plotted to overthrow Lucion, but realizing his master would not back him against Mephisto, Lucion's father, he backed off. After Lucion's strange disappearance at the end of the Birthright novel, Astrogha once more planned to take his place as the Primus, but the strange reappearance of the Primus (this time Lilith) made him abandon his plans. After Astrogha finally realized Lilith was now using the guise of the Primus, Astrogha started scheming against her, even taking the form of the Primus himself for a while. After a short showdown with Lilith, which was only a way to gauge her powers, Astrogha fled the Temple, once again opting for scheming in the shadows.
Moon of the Spider
Appearing once again as a main character of the book, Astrogha remains in an orb called the Moon of the Spider. A prison bound to an unknown dimension, Astrogha was sent there by Vizjerei after his own cult fell. He was then released by a Noble of Westmarch by the name of Aldric Jitan, which Astrogha then tries to lay waste to the capital through his 'Children'. It was only through the efforts of the Necromancer Zayl and the Noble Salene Nesardo, who is revealed to be a descendant of Astrogha himself, that Astrogha was banished back into the Moon.