In certain scenarios the defender has set up sentries to keep a lookout for enemy activity. Sentries can be represented with card counters, but it is preferable to use spare miniatures of the appropriate type. The number of sentries available depends on which army you are commanding and is given on the following list. These sentries do not cost any extra points, nor may they be given any upgrades. Sentries get all applicable army rules that they would normally have access to.
- Orks: 12 Gretchin.
- Imperial Guard: 10 Guardsmen.
- Witch Hunters: 8 Storm Troopers or 6 Sisters of Battle
- Deamon Hunters: 8 Storm Troopers or 5 Grey Knights in Power Armour
- Tyranids: 8 Termagants.
- Eldar: 8 Guardians.
- Space Marines: 6 Space Marines.
- Chaos: 6 Chaos Space Marines.
- Dark Eldar: 6 Dark Eldar Warriors.
- Necrons: 10 Necron Warriors
- Tau: 6 Gun Drones or 8 Kroot
At the start of the sentries' turn, both players roll a dice for each sentry model (or marker). The player that rolls highest can move the sentry the distance indicated on the dice in any direction. If the rolls are tied, then the defender moves the sentry. Sentries do not have any squad coherency rules and operate independently.
For how sentries spot the enemy and raise the alarm, see Sounding The Alarm.