Wamersedari ni watawa wa Shirika la Kifalme, la Kimbingu na la Kijeshi la Bikira Maria wa Huruma na la Ukombozi wa Mateka ambalo lilianzishwa na Petro Nolasco mjini Barcelona, mwaka 1218 ili kukomboa Wakristo waliotekwa na Waislamu kama watumwa. Mojawapo kati ya mambo ya pekee ya shirika hilo ni kwamba tangu mwanzo watawa wake wanaweka nadhiri ya nne ya kukubali kufa kwa ajili ya Mkristo aliye katika hatari ya kupoteza imani, kama ilivyokuwa kwa wale waliotekwa utumwani. Leo shirika linapatikana katika nchi 17. Ann Ball, 2003 Encyclopedia of Catholic Devotions and Practices ISBN 087973910X page 525 Mary's Praise on Every Tongue: A Record of Homage Paid to Our Blessed Lady by Chandlery Peter Joseph 2009 ISBN 111316154X page 181 Homepage for the Order of Our Lady of Mercy in the United States James William Brodman, 1986. Ransoming Captives in Crusader Spain:The Order of Merced on the Christian-Islamic Frontier