Tarasha Euten was the Seneschal to Konor Guilliman and later Primarch Roboute Guilliman. A strong-willed, boisterous, but capable woman, Euten helped raise Guilliman on Macragge. Euten retained her post by the end of the Great Crusade, now elderly and kept alive through rejuvenation treatments. Despite her advanced age, however, she had lost none of her spark, regularly advising Guilliman and even still referring to him as "boy". Despite her fiery personality, Euten was extremely loyal and matronly to Guilliman and the Ultramarines Primarch in turn would share his misgivings and weaknesses with her in private. During the formation of Imperium Secundus, Euten advised that Guilliman crown himself Emperor.
During the Heresy Euten very nearly met her end at the hands of Konrad Curze when the Night Lords Primarch was loose upon Macragge. Curze, wishing to inflict further agony by killing Guilliman's "mother", was first stopped by a pack of Space Wolves led by Faffnr Bludbroder and then by the insane Vulkan, who forced the Night Haunter out of her residence. Later Euten was seen advising Guilliman on how to deal with Lion El'Jonson's defiance and suspicious activities.