Complex sentence: Sickingen became acquainted with Ulrich von Hutten, a humanist Knight, and under his influence his castle of Ebernburg became a centre of Humanist and later Lutheran thinking, with many pamphlets emanating from the castle.
Split into simpler sentences: Sickingen became acquainted with Ulrich von Hutten, a humanist Knight. Under Hutten's influence, Sickingen's castle of Ebernburg became a centre of Humanist and later Lutheran thinking, with many pamphlets emanating from the castle.