El Kulug Shad
El Külüg Shad Irbis Qaghan was khagan of the Western [Turkic Khaganate] in 639 and 640.
Name
While his personal name isn't known, his regnal title was Yiqulishi Yipi Qaghan. Gumilev tried to reconstruct this name as El Kulug Shad Irbis Qaghan. Whilst, the Old [Book of Tang] refers to him as Moheduo Yipi Khagan. The first part of this name is often reconstructed as *Baghatur in Turkic, the nature of the second component is debated. According to Zuev, Yipi was a Chinese rendition of Yelbi, which was a sign of rulers bearing this name being "shaman-kings". According to Marcel Erdal, however, *yelbi was a proto-Turkic term for "sorcery", not a "sorcerer". Another proposed transliteration of his name is Irbis, a name attested many times among Western Turkic regnal names. Minoru Inaba likened this epithet to Nishu, another often shared name among Western Turkic khans.
Biography
El Kulug Shad was a son of Ishbara Tolis Qaghan. In 639, a tudun ''ilteber'' under his father secretly colluded with Yukuk Shad and rebelled, so Ishbara Tolis fled to Bahana where he died. The Nushibi tribes then set up El Kulug Shad as the new khagan but he died in 640. Thereupon, the chieftain of the Nushibi welcomed his cousin Bopu Tegin as the new khagan. He had a son who would later succeed as khagan under the title Irbis Seguy.