Palma, Mallorca, Spain - The solid Golden Monstrance at the Cathedral Sa Seu (built in 1299). A monstrance, also known as ostensorium, is the vessel used in Roman Catholic, Old Catholic and Anglican churches to display the consecrated Eucharistic host, during Eucharistic adoration or Benediction of the Blessed Sacrament. Created in the medieval period for the public display of relics.