In order to start the Fenris quest series you must complete all campaign quests from 1-50.

Boots

Fenris’s Shoes
Fenris’s Leather Shoes
Fenris’s Chain Boots
Fenris’s Plate Boots

After completing all your campaigns, you can now acquire Recognition of the Preceptors from Kvasir in the Capitol Building. The quest is a simple run-around, you do, however have to spend ~4,000,000 kinah on a Glossy Holy Water.

Gloves

Fenris’s Gloves
Fenris’s Leather Gloves
Fenris’s Chain Gloves
Fenris’s Gauntlets

This quest requires you to talk to many NPCs who only spawn at certain times of the day, and do not always spawn.

Speak to Riikaard : Any time of day.
Speak to Herosir : Any time of day.
Speak to Gellner : 7am – 9am.
Speak to Natorp : 5am – 7am.
Speak to Needham : 3am – 5am.
Speak to Landsberg : 2am – 3am.
Speak to Levinard : 1am – 2am.
Speak to Lonergan : 12am – 1am.
Take a Glossy Holy Water to Balder in the Great Temple.
Speak to Kvasir in the Capitol Building.

Pauldrons

Fenris’s Pauldrons
Fenris’s Leather Pauldrons
Fenris’s Chain Pauldrons
Fenris’s Plate Pauldrons

The pauldron quest is quite straightforward. You need to collect 30 Pandaemonium Medals. You can do this by completing either Decorations of Pandaemonium or [Group] The Decorations of Pandaemonium. The former requires you to grind monster for items, it’s handy to also do [Coin] For the Future Settlers at the same time if you need the cash or the Platinum Coins.

For the latter, you can do either Steel Rake, Dark Poeta or Adma Stronghold. As long as you kill the last boss you will loot a Deathmark which can be exchanged for a Pandaemonium Medal.

I will update this guide as I complete the quests myself.