The Antiquarians are some of the Dungeon Armor Set Vendors for Guardians. They can be found in the in the Lodge of the Plains in Sanctum, around 7594, 869, 3100. There are several merchants with the title Antiquarian in the Lodge, all with either a <Holy Relics> or <Consecrated Relics> tag. All of the Antiquarians have the same inventory.
The Antiquarians sell Tier 1 expert dungeon gear which can be purchased using Plaques of Achievement. These plaques are earned by killing bosses inside expert dungeons and completing dungeon daily quests.
This is only a listing of the armor that they carry that has a visible model. They may carry more items such as necklaces, belts, or weapons, but those items are not listed here.