The Seal of Mar is the family crest of the House of Mar, and also serves as an access key in Jak II and Jak 3. The crest resembles a yin-yang sign, although the two components are stacked vertically on top of each other, more closely resembling the number 8. It is found engraved in stone, made of Precursor metal, and as an amulet made of other unknown materials.
The Seal was first seen in the form of an amulet crafted of what appeared to be stone and was worn around the neck of the kid, later discovered to be younger Jak. When Jak visits the pumping station in the mission "Find pumping station patrol", Ashelin Praxis describes to Jak a golden seal engraved in a stone pillar as the family crest of the House of Mar, and that it can open ancient passageways built by Mar.
Later, Jak was instructed by Samos Hagai to find three seal pieces and give them to Onin to construct a full Seal of Mar so that he may use it to activate Mar's gate and enter No Man's Canyon, where he could use the Light Tower to find the Tomb of Mar. The first seal piece was found embedded in ancient Lurker totems in the dig site in the mission "Get seal piece at dig". The next seal piece was given to Jak by Brutter as a gift for helping him. It was left behind in front of Brutter's hut in the Water Slums, and picked up in the mission "Get seal piece at Water Slums". The third and final piece was withheld by Onin, who first made Jak accomplish a challenge before she revealed it to him and finished the Seal of Mar. Once it was completed, Jak had to use it to enter No Man's Canyon in Mountain Temple.
The Seal of Mar design was seen throughout Jak 3 in many Precursor carvings such as throughout the Monk Temple, the crest being the most prominent theme in the areas of the temple. It was also seen, as would be custom, in the eco mine created by Mar. The Seal of Mar as a device was not seen until Ashelin gave one to Jak after protecting her in the oasis. Jak then used this to open a door leading to a set of subrails which led to the eco mine found in the Monk Temple.