As part of their attempt to hire a freighter to transport a stolen Hammertong module, the two Mistryl were masquerading as the Tonnika sisters: Karoly was disguised as Senni Tonnika while Shada posed as Brea Tonnika. Their choice of disguise got them briefly arrested by ColonelParq before being freed by Rebel Alliance agent Riij Winward—although a subsequent disagreement on who should get the Hammertong information saw the Mistryl stealing his freighter to transport the superlaser component, while he made off with their astromech, D4, and a technical readout of the weapon.
During the Hammertong mission, Shada had regarded Karoly as keen but somewhat inexperienced; by 19 ABY, however, Karoly had become a veteran warrior, and she was dispatched by the Eleven Elders of Emberlene to "recover" Shada on Borcorash as the Mistryl made steps to break their ties with Mazzic. Shada escaped, and Karoly's pursuit brought her to Bastion, where she allied herself with MajorGrodin Tierce against her old enemy CaptainZothip of the Cavrilhu Pirates.
Karoly was probably related to Team PrimeManda D'ulin, gunned down in the ambush at the Hammertong base, and also to an earlier Mistryl, Naradan D'ulin.