Complex sentence: A chantry may have just an altar, rather than a chapel, within a larger church, generally dedicated to the donor's favourite saint, and many altars thus became richly endowed, often with gold furnishings and valuable vestments.
Split into simpler sentences: A chantry may have only an altar, rather than a chapel, within a larger church, generally dedicated to the donor's favourite saint. Many altars became richly endowed, often with gold furnishings and valuable vestments.