Description[]
"One of the Four Kingdoms treasures, which rewards the clan with magic when fortifications are built or repaired"
The Antler provides clan magic when you build fortifications (usually one point) or successfully complete the Repair Berenstead venture (usually two points). A failed attempt to repair Berenstead will yield no magic.
Acquisition[]
It can be acquired by exploring Penentan in Lights Going Out.
Lore[]
The antler presumably belonged to an ordeed, a type of antelope considered holy by the Penentelli.