The Brazen Rune

Confers Adamantium Will. 

Once per game at the start of the enemies psychic phase, you can declare that you are using the Runes full power. Until the end of that phase, all psykers within 24" of the bearer suffers Perils of the Warp on the roll of a double. After the phase has ended the model loses Adamantium Will.

A unit that contains at least one model with this special rule receives a +1 bonus to Deny the Witch tests.