Against the Charr

Objectives

 * Examine the Vanguard helmet in Grothmar Wardowns to begin the attack. (disappears from Quest Log after speaking to the Vanguard helmet).
 * Search the Charr camp to the east for signs of the Vanguard captives.
 * OPTIONAL Find ways to weaken the Charr garrison.
 * OPTIONAL Intercept the Charr supply caravan. Use explosive charges to disable it.
 * OPTIONAL Destroy the watchtowers with explosive charges. 0...2 of 2 destroyed.
 * OPTIONAL Employ the siege devourers to fire explosive charges at the garrison. 0...2 of 2 fired.
 * Defeat Harvest Soulreign.

Obtained from
 * Automatically added upon completing Search for the Ebon Vanguard
 * After first completion, can be obtained from:
 * Vanguard Helmet in Grothmar Wardowns
 * Scrying Pool in Hall of Monuments (select "I seek guidance" option)

Requirements
 * Search for the Ebon Vanguard

Follow up
 * The Dawn of Rebellion

Walkthrough
Leave Longeye's Ledge and head southeast to find a battlefield crawling with Carrion Feeders and Stonewolves, with a lone Vanguard Helmet in the middle. Speak to the helmet to initiate the quest.

All you have to do is fight your way to the Charr camp, storm it, and defeat Harvest Soulreign; everything else is optional. However, completing the optional objectives will reduce the number of Charr in the camp, cutting the garrison by half if you complete all five objectives. All of the optional objectives involve blowing stuff up, which can be quite rewarding in itself.

During this quest, you will encounter Charr Firereigners in many of the enemy groups, who each drop a Charr Explosive when they die. These are required to complete the optional objectives and can also be used against the Charr themselves, much like Dwarven Powder Kegs.

The easiest path to the camp is to run south from the starting point and cross the southern bridge, then follow the southern edge of the area until you come to the large river. Avoid the Charr around the Siege Devourer as you head north to the garrison. Harvest Soulreign is in the rear of the camp accompanied by Gordam Griefgiver, but only Harvest needs to be killed to complete the quest. When he dies, a cutscene will play, after which the party will reappear in the now-empty Charr camp with Pyre Fierceshot as an ally.

Optional objectives
Intercept the Charr Supply Caravan: The caravan is the northwestern red icon on your mission map (U). Simply drop a Charr Explosive near any one of the supply carts to destroy the entire caravan. The nearby Ammo Cart will supply you with unlimited Charr Explosives.

Destroy the Watchtowers with Explosives: The other two red icons are the watchtowers. Drop a Charr Explosive next to each of them to burn them down.

Employ the siege devourers to fire explosive charges at the garrison: The Siege Devourers are at the two star icons on the map. While carrying a Charr Explosive, speak to the devourer to load the charge. After lobbing the charge at the garrison, a return volley will take out the devourer.

Hard mode
Hard mode makes the Charr a lot stronger, but doesn't change the basic tactics. The strongest enemy group is the group of six that will charge your position at the start of the mission. They can be avoided by looping clockwise around the large stone formation just west of your starting location, and then you can proceed with the mission as normal.

Monsters

 * Charr
 * 20 (26) Charr Axemaster
 * 20 (26) Charr Blademaster
 * 20 (26) Charr Seeker
 * 20 (26) Charr Prophet
 * 20 (26) Charr Hexreaper
 * 20 (26) Charr Dominator
 * 20 (26) Charr Firereigner
 * 20 (26) Charr Flameshielder
 * Mantis
 * 20 (26) Mantid Queen
 * 20 (26) Mantid Nymph
 * 20 (26) Mantid Digger
 * Mandragor
 * 24 (26) Mandragor Dust Devil
 * 24 (26) Mandragor Smoke Devil
 * 24 (26) Vile Mandragor
 * 24 (26) Mandragor Shadowfang
 * Skale
 * 24 (26) Swampwater Skale
 * 24 (26) Deadly Skale
 * 24 (26) Skale Lasher

Bosses

 * Charr
 * 24(30) Groknar Weazlewortz (Barrage) - at Supply Caravan
 * 24(30) Anmat the Trickster (Power Block) - at northern Siege Devourer
 * 24(30) Frazar Frostfur (Ward Against Harm) - at southern Siege Devourer
 * 24(30) Gordam Griefgiver (Eviscerate) - in central fort
 * 24(30) Harvest Soulreign (Spiteful Spirit) - in central fort (killing him ends mission, impossible to capture from)

Dialogues
Briefing from the Scrying Pool.