In Grenth's Defense

Overview
Summary
 * 1) Speak to the Rift Warden when you are ready to defend the Underworld.
 * 2) Destroy all followers of Dwayna who attempt to breach the Underworld. They must not reclaim the stolen presents.
 * 3) See Rift Warden for your reward.
 * * BONUS*: Survive for as long as possible.

Obtained from
 * Rift Warden in Kamadan, Jewel of Istan.
 * or
 * Rift Warden in Lion's Arch.

Reward
 * 1,000 Experience
 * 5 Candy Cane Shards

Dialogue
 * ''"Grenth's legions have been busy this year...perhaps more so than any in the past. They've nicked countless presents meant for the good children of the world and stashed them deep within the Underworld. As we speak, Dwayna's followers have mustered to recover them. Grenth requests your dedication; guard the presents to your dying breath. Do you accept the Lord of the Underworld's challenge?
 * Accept: No child will be smiling this Wintersday. Grenth can count on me!"''
 * Reject: I think I hear Dwayna calling....

Intermediate Dialogue (Avatar of Grenth)
 * "You have done well in your service to Grenth. Your situation in the afterlife is no doubt assured, however the Mists will have to wait... for now. Do you wish to return to the realm of the living?"
 * Take me to Lion's Arch.
 * Take me to Kamadan (sic)
 * I want to play the bonus challenge.

Reward Dialogue
 * "Word of your service has already spread throughout the Underworld. Perhaps Grenth will emerge victorious with you on his side."

Walkthrough

 * Upon entering the Underworld, all other party members are removed and your skills are replaced with the snow fighting skills.
 * You must defend the stolen presents from 24 level 15 Snowmen of various professions, as well as a level 19 boss named Freezie.
 * Using Hidden Rock is a great strategy to Daze snowmen, so use it after every fight.
 * Use Yellow Snow to get rid of conditions,
 * Use the Warrior's Shout "Let's Get Em'!" to charge the Mega Snowball and outrun Snowballs when your skills are recharging from "Mmmmm, Snowcone!".
 * Consider using a Ritualist and cast Jack Frost. Keep Jack Frost up at all times to take damage and use Hidden Rock and then a Snowball to shut the enemy down. If you don't have a Ritualist in Kamadan or LA a Monk is another fine choice.
 * Rangers also work well. Cast Yellow Snow prior to each attack and constantly spam Flurry of Ice. Don't kite or move around, just fight outright. Use Ice Fort and "Mmmm. Snowcone!" as required.
 * Upon finishing the mission an Avatar of Grenth appears. It offers to send you back to town or you can try the bonus, which is to defend the presents for as long as possible. There are 6 rounds of this bonus, each containing 6 Snowmen of various types. You receive one Candy Cane Shard for each completed wave. The waves are as follows:
 * Wave1: Snowman, Snowman, Snowman, Mischevious, Roguish, Bustling.
 * Wave2: Grumpy, Grumpy, Grumpy, Chilled, Pious, Playfull.
 * Wave3: Roguish, Industrial, Roguish, Impeccable, Glimmering, Blessed.
 * Wave4: Industrious, Playfull, Playfull, Cordial, Chilled, Rotund.
 * Wave5: Industrious, Playfull, Playfull, Cordial, Chilled, Pious.
 * Wave6: Industrious, Playfull, Playfull, Cordial, Chilled, Rotund.

Also

 * it was possible to exploit this quest by accepting it when you are a lower lvl for example lvl 2 in Kamadan and get yourself up levels quick because your health and stuff is set and the Snowmen are lvl 15-24 and the Snowman Boss, Freezie is 19 so it is an easy lvl up, but don't do this if you are trying to get survivor because you are most likely to die.