The article is an attempt to answer the question what was the potestas Legnicensis mentioned in 1175 in the document of Bolesław I the Tall for the Cistercian Abbey in Lubiąż. The author is against the thesis that she was a synonym of the Castellany in Legnica, indicating that at that time there were no still castellans in Silesia. Pointing to the evident institutional relationship of this potestas with the Legnica residence of Henry I the Bearded, concentration of evidence of efforts to build a strong foundation of power in the Legnica region, and supporting Janusz Bieniak’s thesis on political development in the Piast dynasty in the years 1177–1202, the autor claims that the mysterious unit mentioned for the first time in the document from 1175 was an attempt by Bolesław I the Tall (probably based on the pre-existing “Legnica territory”) to create a strong “stepping stone” for his son and successor. It was the Legnica territory that constituted the base on which he based his efforts to succeed father Henry I the Bearded. His first step in great politics was the extension of the status of Legnica – family power, unrestrained by the claims of other Piasts – to Wrocław and Głogów territories by buying the senior rights of Mieszko I Tanglefoot. This step gives Legnica potestas a pioneering feature – because it seems that it was from Legnica that Piastowice began building completely sovereign powersjurisdiction.