Pekka is a Kuusaman mage. In her researches into the basic principles of magic, she discovers a revolutionary principle, and becomes one of the leading researchers in the project to develop a super-weapon based on this principle, to her surprise being accepted as an equal by Ilmarinen and Siuntio, the greatest theoretical mages of their age . Eventually she assumes direction of the "Naantali Distinct Project" where the weapon is being completed.
A highly sympathetic character, warm-hearted, humorous, a devoted mother and a loyal wife, she agonises for over three volumes about having fallen in love with Fernao without falling out of love with her husband Leino - a dilemma solved tragically only when Algarvians kill Leino in a magical battle.
Yet at the same time, Pekka gives her all to developing the most fearsome weapon her world has ever seen - with the best of motives, the apprehension that Algarvians may find it first and the urgent need to find a "clean" counterbalance to the Algarvian murder-powered magic. Eventually she gets to use the weapon herself, together with her beloved Fernao and with Illmarinen releasing enormous sorcerous energy upon the Gyongyosian capital Gyovar, killing in a single instant all its inhabitants, including tens of thousands of other mothers and their children. As a mage, she could actually feel the anguish and death of her victims.
Immediately afterwards, she and Fernao have a rather bland wedding ceremony and settle down to domestic bliss in a nice provincial town, seeming not too deeply haunted by what they had done.
The Darkness series is modeled on the Second World War. In this framework, Pekka's dicovery is the equivalent of the splitting of the atom and the Naantali Distinct Project where it is made into a weapon is the Manhatten Project. Pekka's role as both the administrative and scientific director combines the roles of Leslie Groves and Robert Oppenheimer. Since she is also the one who actually unleashes the weapon on the target city, she also has the role of Colonel (later General) Paul W. Tibbets, Jr., commander of the plane Enola Gay which dropped the first atomic bomb and destroyed Hiroshima.
"Pekka", like other Kuusaman names, is taken from Finnish. To non-Finnish readers, it is a plausible woman's name, but actually it is a typical male name, the Finnish equivalent to "Peter" (the female version should be "Pekki". In fact, some of Finland's neighbours use it as a derogatory nickname referring to a drunken/bad-mannered Finnish tourist. It is unclear whether Turtledove was aware of this when he gave the name to a female character.