Mirthen was an addict to the narcotic Waste-it, commonly carrying two sticks of it along with his comlink and a blaster he could hardly use. He was however quite adept in weaponless fighting, starship gunnery, and survival in water environments. Nevertheless, Jayhawk had not promoted him because of this; he did because Mirthen was unambitious and would not conspire to replace Jayhawk.
Mirthen was onboard the Martinette on 1 ABY, when Jayhawk ordered to attack the pleasure yacht Long Shot.