One of the most important victories of the magnates was the late 16th century right to create ordynacja's (similar to majorats), which ensured that a family which gained wealth and power could more easily preserve this. Ordynacje's of families of Radziwiłł, Zamoyski, Potocki or Lubomirski often rivalled the <answer>estates of the king</answer> and were important power bases for the magnates.
What was an important power basis for the magnates?
estates of the king