At the start of each of your turns, choose a friendly monster within 6" of the Beastmaster. That monster has +D3 Attacks until the start of your next turn. A monster can only be affected by this special rule once in each turn.
Source: Warhammer Armies Project: Unofficial 9th Edition (v2.2)
At the start of each of your turns, choose a friendly monster within 6" of the Beastmaster. That monster has +D3 Attacks until the start of your next turn. A monster can only be affected by this special rule once in each turn.