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At the start there are groups of Minotaurs to defeat including an unnamed Minotaur boss. Be careful around this area and try not to aggro too many at once, since they are strong enough to kill you in large numbers and they charge toward you as you approach the area.

The ballistas are easy to find, since destroying each one opens a gate allowing you to travel further south. Also, whenever a ballista strikes, you will see a flashing spot on your map showing where it was fired from. In order to destroy a ballista, kill the Stone Summit Engineer next to it. The ballistas are located at the points marked A on the map. Continue south until you reach point B on the map, where you will find a Gear Lever. Bring the lever to the gate in order to open it.

Once it is open, you will be faced with a few groups of Stone Summit guarding the three mechanisms. Clear the area and then put the Gear Lever into 3 winches, which together open the frost gate and complete the mission (point C on the map). The first one you activate opens a gate for mobs to come from the south. The second opens an analogous gate for mobs to come from the west. The third starts an invisible 60 second timer, and when that ends, you win the mission. The order in which you use the lever mechanisms doesn’t matter for these mechanics.

When you open a gate with mobs behind it, a group of three mobs (often including a boss) will come through it to attack you, then after a bit of a pause, two more mobs come. There is a longer pause, then two more mobs, and another small group or two after additional short pauses. The longer pause after the second group is enough for you to trigger one lever, kill the first two groups, then go trigger the other two levers and easily be able to survive the remaining 60 seconds. If the battle is going really badly after you’ve used all three lever mechanisms, you can survive by simply running away.

Note: When your lever carrier puts the lever into a mechanism, he/she will lose the lever for a few seconds while the mechanism is started. The lever will then be dropped next to the mechanism. So, make sure they stand and wait for it to drop.

Note: If lever mechanisms aren't activated after a while, Rurik will be overwhelmed and defeated. Although the mission objective says to activate the three Frost Gate lever mechanisms before Rurik dies, the mission nonetheless can be completed after inserting the Gear Lever into the third mechanism despite Rurik being a corpse. During the cut scene that follows, he will be shown to be alive rather than dead.

Tip 1: If you have cleared the two groups that are initially guarding the mechanisms, you can then move the rest of your party to the gate where the Summit are coming from and engage them. This leaves the three mechanisms clear for your lever carrier to operate them unmolested.

Tip 2: After reaching the area with the three lever mechanisms, you may drop the gear lever and go hunt the very large number of Stone Summit in a canyon-like area off the main path. While difficult, defeating them all will ensure you go about operating the mechanisms with minimal interference. Additionally, after operating one mechanism, a gate opens which allows for several more enemies to enter. With careful pulling you can pick them all off. If both of these are done, you will practically ensure the success of the mission, although time should be taken into consideration.

Bonus
The bonus mission is triggered by rescuing Rornak Stonesledge from the Frostfire Dryder caves (point 1 on the map). Be careful when engaging the dryders, as they can place a great burden on healers with their use of the Suffering spell. Rornak will ask you to help him retrieve some Secret Siege Weapon Plans from the Stone Summit dwarves nearby. Exit west from the cave, and you will find a group of Stone Summit fighting a group of Ettins. Beyond them will be a crater area where the ballista fire lands. In that crater, you will notice a small opening to your right (the path to point 2 on the map); follow that path. Beware of two groups of Stone Summit there; if they are together, they will pose a significant challenge, especially with several Dolyak Riders healing each other and the Summit. Defeat them and go up the road to the ballista. Rornak will fix it and you can fire the ballista to open a gate on the other side. Afterwards, go back to the crater area, head across the bridge and enter the now opened door. Proceed up the mountain and retrieve the plans (point 3 on the map). Run the plans back to Rornak (point 2 on the map).

Tip 1: The cleanest way to complete the bonus is to avoid Rornak until you've cleared out both the area across the bridge, and the path leading to the derelict ballista. Then talk to him, walk him down, leave him at the ballista, and go get the plans.

Tip 2: Skills that do AoE damage, or that debuff (Necromancer and Mesmer skills, for example) can make the fight with the dwarves guarding the ballista (point 2) a lot easier. Remember to focus on defeating any Dolyak Riders first. If they are clustered together, try pulling them away from each other back up the path and eliminating them one by one.

Tip 3: The plans at point 3 on the map are mainly guarded by Ice Golems. They are highly susceptible to Fire Storm, Fireball and other fire AoE spells, as they take double Fire damage. Also a Fiery upgrade for your weapon will do miracles.

Tip 4: When you approach the now destroyed door, a big pack of Ice Golems and some Summit will come and guard the place where the door used to be. As they are all packed in, you can now return to the ballista and fire it as many times as necessary. When you come back all baddies will have been swept away. Keep in mind though that as usual with ballistas you won't get any XP or drops.

You must talk to Rornak once you have the plans, or you will not be awarded the bonus. This must be done before triggering the cut-scene (point B on the map), or you will lose the plans. Alternately, you can trigger the cut-scene before picking up the plans, and then go talk to Rornak to obtain the bonus.