The Order of the Silver Seal is a smaller order based primarily out of Breland dedicated to wiping out aberrant cults of the dragon below. The order was formed three centuries ago when the templar Selsharra Derissor was trailing down a set of mysterious disappearances, meeting and joining forces with a Gatekeeper sect who revealed and explained the aberrant threat. Selsharra did not convert to the druidic practice, but took her knowledge and founded a new order. It is now led by Cardinal Ildrazar, a half-orc hailing from the Shadow Marches.
Source: Politics of Thrane
The Order of the Silver Seal is one of the smallest orders of the Knights Templar and is primarily active in Breland. It is dedicated to combating aberrant forces, and Cults of the Dragon Below. The order was formed three hundred years ago when a group of templars were investigating a mysterious set of disappearances joined forces with a Gatekeeper sect who revealed and explained the aberrant threat. The templars did not wholly convert to the druidic practices of the Gatekeepers but took the knowledge they gained from working with them and founded a new order that blended their traditions with those of the Church. It is now led by Knight-Commander Ildrazar (female halforc druid, she/her), a half-orc from the Shadow Marches.
Source: Sarhain's Guide to the Silver Flame