During “The Sapphire Tablet” quest, whilst in The Ruined Coast - you interact with a bridge lever before collecting the Tablet, before the Temporal Sanctum.
When facing Ortr’ek the Survivor miniboss - he cannot travel across the bridge, nor can your minions cross the bridge due to an invisible wall.
If you run back far enough, minions/ranged attacks can just cheese the boss without being in range of attacks.