From Warhammer 40k - Lexicanum
Grey Crest is a relic of the Leagues of Votann.
This cunningly wrought armour crest contains helical circuit-threads believed to have been traded from a mysterious alien race long since lost. It projects a veil of energies able to fool both organic and artificial targeting senses, concealing the wearer.
- 1: Codex: Leagues of Votann, pg. 66