Two Saradominist sentries are guarding the camp of Saradomin during the Battle of Lumbridge. They will fire explosive-tipped arrows into any Zamorakian soldier that runs into the Saradominist camp. After about two seconds, the arrow explodes, instantly depleting all the Zamorakian soldier's health. If no players have attacked the Zamorakian soldier, the arrow will do 10000 damage, making Saradominist sentries (along with Zamorakian sentries) by far the most powerful NPC on the Lumbridge battlefield and possibly in the game.
The sentries themselves cannot be talked to or interacted with at all by players. They remain in permanent combat stances and upon detecting an enemy they will calmly shoot him or her and then casually face forward again.
Sentries do not attack Champions, and explosive damage is not dealt towards them.