Two Zamorakian sentries are guarding the camp of Zamorak during the Battle of Lumbridge. They will fire explosive-tipped arrows into any Saradominist soldiers that runs into the Zamorakian camp. After about two seconds, the arrow explodes, instantly depleting all the Saradominist soldier's health. If the no player have attacked the Saradominist soldier, the arrow will do 10000 damage, making Zamorakian sentries (along with Saradominist sentries) by far the most powerful NPC on the Lumbridge battlefield.
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 them and then casually face forward again.
Sentries do not attack Champions, and explosive damage is not dealt towards them.