If Redmaw the Chaos Warhound is included in your army he forms a unit with Khazrak, though they may both join other units as normal. If Khazrak is slain, Redmaw is subject to Hatred and Frenzy for the remainder of the game.
Source: Warhammer Armies Project: Unofficial 9th Edition (v2.2)
If Redmaw the Chaos Warhound is included in your army he forms a unit with Khazrak, though they may both join other units as normal. If Khazrak is slain, Redmaw is subject to Hatred and Frenzy for the remainder of the game.