Sunstone Sentries are fought in the Fortress of Solitude: Sunstone Matrix raid, in which they are summoned in pairs to aid Non, Ursa or General Zod.
There are two types of sunstone sentries. The red type is very weak and only hits for about 300, but the golden type has a very power melee attack that hits over 2000s, as well as a long-ranged grounding attack. When the latter type appears, they should be kited and lured away. They must not be allowed to approach the boss or they would easily destroy the dps players clustered around the boss.