Rockstrum (ロクストラム, Rokusutoramu) is a location in Genso Suikoden Tierkreis Hoshikuzu no Shiro.
Rockstrum was the city of the Biskiel people and came to this world through the process of world fusion. As such, it contained the vast majority of the dwindling Biskiel population.
Its governance following world fusion was largely unknown, but as Cario was still referred to as a councilor, its old governing body may have survived in some form.
The Biskiel tended not to have children and none are younger than Cario. This is generally because of a fatalistic view that the Biskiel were fated to die out.