It is possible to open the barred gate in Area 1, Path 1 without going through the left path. Use an area of effect attack to the right side of the gate to hit the nearby switch.
As soon as Kalis spawns, run to the entrance of the room. If you run quickly enough, the Servant will not notice you.
The Servant of Hell is considered a Sub Boss, and it isn't required to be killed to complete the battle.
Notes
There is one ore deposit in Area 1, Path 2 in the northeast corner of the final room.
As soon as the party reaches the final room, Ellis can be seen up ahead with his clothes scathed and heavily wounded. He walks a few feet and collapses, crawling. Soon, Information Chief Kalis bursts through the tombstone behind him and growls. The Goblin then circles the wounded human as the players fight off multiple spawns. After defeating the minions, Kalis picks up Ellis by the leg and tosses him. The Goblin then picks up the squirming human by the head and stares at him. After growling and looking around, Kalis brutally murders Ellis by smashing him on the tombstone in front of him three times. Kalis then tosses the lifeless body through the gate and jumps, growling at the expedition.