Tagichatn may not be the correct spelling of his name, since Vlad Taltos could never remember it exactly (alternate spellings he offers include: Takishat,Tagijatn, Tadishat, and Taishatinin).
Tagichatn was killed by Vlad shortly after assuming control of his territory, mostly since Vlad couldn't stand working for him.
Despite Tagichatn's low status in the Jhereg Organization, he had purchased (no doubt at great cost) the title of a Duke in the House Jhereg nobility, which prompted The Empire to investigate his death. Skillful dodging of certain questions under the Orb allowed Vlad to escape this investigation unscathed.
Call me God-Boss