The Moonlit Path/Strategies

Tips
Fenrir is most powerful during full moon, it is recommended to not do this battle during this time. (It is not impossible, just more difficult.)

Like the other avatars, he will use Howling Moon at 50% HP. However, unlike the others this does not mean you're out of the woods as he will use it again at 30% (found this out the hard way so I thought I'd share)

Shield Bash can stun his 2 hours.

Working Job Combinations
This section is not meant to discourage people from trying different combinations, but to illustrate combinations that have been tried and tested. Please feel free to try this BCNM with any combination you think might work, and above all, have fun!
 * Exp Party setup with Paladin tank
 * 4-6 70+Summoner
 * EXP Party setup with Ninja tank

Exp Party with Paladin Tank
Strategy:
 * This is as if you were in an Exp party, except it is even more crucial that the tank maintains hate.
 * Keep the tank alive. (Fenrir hits pretty hard)
 * Have the tank maintain hate. (High enmity recommended.)
 * NIN sub for Paladin helps, Fenrir's normal hits shouldn't be taken directly if possible. Keep a shield in off-hand, Shield Mastery can mean the difference between life or death for recasting shadows, especially in the case of a badly timed Lunar Cry.
 * Stun his 2 hours with Shield Bash, and if he does it again at 30%, stun with Weapon Bash or a stun WS, they are less likely to be resisted then the spell stun.

Strategy Pros:
 * Easy to setup this style of party.
 * Lunar Cry doesn't need to be stunned in such a setup.

Strategy Cons:
 * Safety is not guaranteed.
 * The stuns are never 100%.
 * Fenrir's high damage makes it harder for a Paladin tank to straight tank everything (Eclipse Bite can do upwards of 600 damage on a Hume Paladin with the Adaman set)

Making this Strategy Better:
 * Healing items, such as Hi-Potions, are recommended for anyone meleeing.
 * Bring a bard for dark carol.
 * Though Fenrir is very resistant, you can try to find someone with high dark magic skill to try to stun Fenrir's 2hr. Alternatively, get a DRK for Weapon Bash.

Summoner Party
Strategy:
 * Summon preferred avatar (usually Titan or Leviathan) and use its lvl 70 Blood Pact.
 * Stay at a safe distance until 2-hour is used.
 * Resummon avatars as necessary.

Strategy Pros:
 * Simple

Strategy Cons:
 * Requires that you have summoner leveled, or a group of summoners willing to let you leech the battle.

EXP Party with Ninja Tank

 * Setup tested with - 75Ninja/37Warrior, 75Samurai/37Dark Knight, 75Summoner/37White Mage, 75Red Mage/37Black Mage, and a 61Summoner/30White Mage.
 * No two hours were required.
 * Ninja and Samurai trade off hate - using alternating Provoke from the Ninja, and a Weapon Skill from the Samurai - while the Red Mage enfeebles Fenrir Prime and heals the party, with the assistance of the Black Mage. Haste for the Ninja and Refresh for the 75Summoner should take priority over Refresh for anything else.
 * Summoners DD with Leviathan Blood Pact: Rage.
 * It is necessary to recast buffs a lot, in most cases. Fenrir Prime can Dispel all buffs, including Reraise, so be prepared.
 * It is necessary to Stun Fenrir Prime's Howling Moon two-hour, which he uses at roughly 50% HP, and to Stun Lunar Roar.
 * Continuing in this fashion is an almost guaranteed win.