Galgast originated from a drow host of House Oblodra in 1358 DR and the psionic powers of his host permitted the birth of an ulitharid. Later in the same year, Methil El-Viddenvelp disappeared in the wake of the drow defeat in the assault on Mithral Hall. It was only natural that Galgast assumed the leadership of the Sept, which he led from that point on.
Galgast considered himself the natural leader of his fellows and used them as subordinates, and this was true: in illithid society, only the elder brain was more revered than an ulitharid. He inherited the will of Methil and was determined to finish his work of creating a new elder brain.