geas

noun2

1. •
   A (generally magical) vow, obligation or injunction placed upon someone to do or not do something, which typically brings harm if violated and blessings if obeyed.

   • It can send us where it will with a task laid upon us—a geas, if you like. — 1989
2. •
   A mystical compulsion.

   • The memory came upon him like a geas, overwhelming his revulsion, numbing his heart. — 1980