Determiner-12 is a spell within the Briarverse.
Endri and Bash discovered Determiner-12 after accompanying Ascender to Monarch’s Manor, where they worked to restore the Monarchs’ old library databases in an attempt to find protection stronger than the Joradian Non-Material Safeguard, which was failing as magic drained from the Book of Kings.
In the shards of Ascender’s memory discovered through the Peering Arts spell during the Search for Magiq, Determiner-12 was explained to be a proxy that could provide “three-tier protection against both physical and virtual places and groups” while “leaving room for the practitioner’s intention and discretion.” The spell would establish an entity to continuously determine who would be permitted access to the protected places and people, and was incredibly dangerous, being an incomplete combination of at least twelve other spells. No one at Monarch’s Mountain had ever known a practitioner to survive the casting in the decade they had spent researching it.
Ascender volunteered to cast the spell on the Manor, claiming that he knew of a “bearer’s band” that had been found by the ‘94 Mountaineers and would protect him. Believing the band to be a ruse and Ascender’s real intention to sacrifice himself, Endri requested that should the spell begin to fail, Ascender would attempt to redirect it to protect the Mountaineers, using the Guide to Magiq as the determiner. The consequential obscuration of the Mountaineers and the forum suggest that this is what happened, and though Ascender failed to protect the Manor, he succeeded in placing a “leaden veil” around the Mountaineers and protecting them from the harmful forces of the outside world to which they would have been otherwise vulnerable during the last days of the Book of Kings, after the Joradian failed.