Thu'karam¶
Thu'karam was an Orc summoner of the Age of Magic who opened "the first recorded abyssal rift" and began the First Rift War (1689 to 1804 MA). He conquered the north with demons, let two archdemons through, and was destroyed by the host he had called (S386, S372).
The rift¶
"The demons at first obeyed him and helped him conquer Theraec and most of the north" of Numenia. Then "the demons were able to convince Thu'karam to widen the rift and allow more of their brothers through, including two arch-demons, Mephistus and Asmodean" (S386, S372). The Abyss had been sealed since the Abscission; only after the Shattering weakened the barrier could "small holes" be punched in it by demonic summoning (S386), and Thu'karam's is the first such breach the histories record.
Downfall¶
"Overestimating his control of the demons proved to be his undoing and his horde of demons turned on him and his Orcish army" (S386, S372). The histories do not say how he died. The demons he had loosed spilled south into the lands that became the Empire of Thyssia and were held for seventy years along the Dragonspine and Cloudhall ranges, until the archdemons were slain at Arne-Athosia; the rest of the war is told on its own page.
Gap
No source gives Thu'karam's clan or homeland, when in the war he died, or how he learned to open a rift. The rift's location is not named beyond "the north".