Tutorial: Mission Battles

This entry is written entirely from my personal experience or those of friends.  If a battle's not here, I haven't done it yet.

All battles require a full clan of 501, and your chances are greatly increased if you've done a recent powers check!

Mission battles provide heads as trophies, located in your Catacombs.

Eliminate the Slayer Chapter 1/5 Act 2/2 : "You thought it was a silly notion: a mere mortal killing Vampires... but it is true. Now you have been instructed to hunt and kill this "slayer". It will be no easy task, but you must complete it."

Costs 12 Energy, 10 Clan, 1 Rage per hit.

You probably will NOT be able to complete this mission when you first open it. Bypass it and come back to it. Common advice is to wait until you have 65 for Attack and Defense and 12-15 Rage.  I did it with 62 Defense and 65 Attack and 15 Rage.  One elder recommends a minimum of 60 Defense (Drakul's Armor can bump you up) and 65 Attack (Fists of Caine can bump you up), and 12 Rage.
Must be killed four times to master the mission.

Slaughter a gang leader Chapter 3/4 Act 2/2: "Sometimes the only way to sever a threat is by taking a head. You don't mind... it's one of your favorite pastimes. This time it will be the head of the gang leader. That should stop them."

 Costs 32 Energy, 30 Clan, 1 Rage per Hit.

You probably will NOT be able to complete this mission when you first open it.  Bypass it and come back to it.  I've heard you need a minimum of 120 each for Attack and Defense, and 13-15 Rage.  I barely beat him a single time with 111 each in Attack and Defense, 100 Health, 30 Energy (I had collected off a shout-out box to get to the required 32), and 15 rage. I killed him the fifth time (it was still close!), with 123 attack and 129 defense at level 59, taking about 11 of my rage, and right after an energy BBE to get to 32 energy (BBE explained a bit here and a bit here).
Must be killed five times to master the mission.

Battle the Lycan Leader Chapter 2/3 Act 3/3: "It's [sic] giant frame looms before you, angry and snarling... but you fear not. Should you only conquer this ferocious creature, your place in the vampire legends is assured!"

Costs 45 Energy, 100 Clan, 1 Rage per Hit, 10 Lightning Speed.

This is unlocked when you have completed "Ambush the Lycans Chapter 2/3 Act 2/3," which costs 40 energy and 100 clan itself.  Not having the required energy to have even unlocked it yet, I haven't completed it myself.  A respected elder tells me it requires at least 220 Lightning Speed.  One of my Northman sisters was able to beat the Lycan Leader while she was in the mid-60s with an attack of 130, a defense of 134, and 15 rage.  She reports that it was a close call, though!
Must be killed six times to master the mission.