A model bearing a holy relic may reveal it once per battle. This may be done at any time, as long as the model with the relic does not move during the same turn it is revealed. On the turn the relic is revealed all models in the Daemonhunters army within 2D6" get a +1 Attack bonus for the rest of that turn. Note that the relic may be revealed in an opposing player's turn if you wish. One per army.
Errata — Chapter Approved: Codex: Daemonhunters Q&A (v1.0): An effect with a radius like this one, described as affecting "all friendly models," also affects units taken from an allied or inducted list fighting alongside the Daemonhunters.