Ida began following Lief, Barda and Jasmine after they left Dread Mountain and continued to follow the group for days, pretending to be simple wood mice. They eventually moved ahead of the group and staged a trap, taking the forms of young twin sisters. They leaped into the River Tor, pretending to have fallen from their raft and Ida cried out Marie's name in fear, alerting Lief, Barda and Jasmine.
Lief rescued Ida while Barda dove to rescue Marie, who had fallen into deeper water. Ida wailed for her seemingly drowned "sister", asking to be taken away from the River and the sight of Marie’s body. Jasmine began to lead Ida away as Barda attempted to resuscitate Marie. Before the two Ols could fully separate the group, however, Ida was shot in the back with an arrow. "She" died instantly, falling to the ground without a sound and the Ol's body disappeared shortly thereafter. Lief charged at the archer, Dain, but Marie took the distraction to catch Barda off-guard.
Marie and Ida were the first Ols that Lief, Barda and Jasmine knew that they had encountered, making them more cautious of their surroundings in the future. Dain managed to gain the group's trust because of his help in killing Marie and Ida, furthering one of the Shadow Lord's numerous plans.
Ida's primary form was that of a young girl, seemingly around five or six years of age. "She" sported straight brown hair, a heart-shaped face, long, curling black eyelashes, and golden skin. The Shadow Lord's mark was disguised as a small, brown birthmark on Ida’s left cheekbone. Ida wore a plain, white dress and was an identical twin to Marie.
Ida could change shape to match the appearance of any living creature and was known to have taken the form of a wood mouse to spy on travellers. Ida's true form was presumably the same as all Ols: a large, white creature with the Shadow Lord’s mark at its core.
Ida put on the personality of a frightened young girl, crying often and mourning her supposedly dead "sister". This persona was an act, however, Ida was, in actuality, a loyal servant of the Shadow Lord, willing to do anything to stop threats to his rule.
As a Grade One Ol, Ida's powers were imperfect, but effective. It could take the form of any living creature, regardless of size. Like all Grade One Ols, Ida could not hold a stable form for very long before being briefly overtaken by the Tremor. Ida could not eat or drink, nor could it hide its unnaturally cold body temperature, though Ida and Marie were clever enough to pretend to have fallen into cold water, giving them a valid excuse. Ida was a moderately talented actress, able to fool even the normally suspicious Jasmine. Ida’s weakness was its heart, located in the right side of its chest.