Guild Wars 2  - Help Warden Brulians Destroy Undead and Crush Any Plague-Spreading Plants

“Defeat Undead, clear corrupted grub holes, and destroy Orrian articles around Morgan's Spiral.”

Head over to the West of Morgan's Sprial. Up the slope you will find Wardne Burlians who you would want to talk with to get more details on this quest.
Brulians: “I've served the Wardens since my awakening. My path has never shifted and my heart has never wavered. I was born to protect.”
Hero: A) “What can I do for you?” B) “Tell me about this place.”
Burlians A) “The undead scour the beach for life to consume. Destroy any undead you come across, and crush any noxious plants that spread their plague.”
Burlians B) “This beach is a hotbed for undead. They wash in from the sea, some even originating from Orr itself. We constructed the spiral as a seedbed for mortar pods to help us defend the area.”

Just wandering around the area you will find no lack of Risen in any variety. Just defeat them either singly or in groups to fill up your track rapidly. There is hardly any need to look for long to find them. If you find an undead corpse you have the option to burn it. Doing so will get it to rise up and attack you.

Around the area you will notice small plumes of green smoke. These mark the Corrupted Grub Holes on your map. Stomp them down and a lvl. 5 Risen Grub will rise from the ground and attack your hero.

Along the Spiral you will also find various seed pods. Interact with them to get the Mortar pods to bloom. If there area's event triggers with a massive invasion of Undead these are a great aid.

After the track has been filled it is on to receiving the letter from Warden Brulians containing 56 copper.
“Sending you aqll my best thoughts and wishes for your happiness and security, Hero's Name. I am in your debt. Our little undead problem seems to have abated slight, but we still have much work to do. We've a head start, thanks to you. - Warden Brulians”