Complex sentence: Mary of Guelders (c.1434--1 December 1463) was Queen Consort to James II of Scotland, and the Regent of Scotland from 1460 to 1463.
Split into simpler sentences: Mary of Guelders (c.1434--1 December 1463) was the Queen Consort of Scotland as the spouse of king James II of Scotland. She served as Regent of Scotland from 1460 to 1463.