What is Living End?
I really like the nice split between Aggro and Combo in Jund colors. The basis of the combo is to cycle creatures and then resolve a Living End which wipes their bored and brings back all of your cycled creatures. This usually occurs by casting a spell with cascade (either Demonic Dread or Violent Outburst) which will always find a Living End.
Why run Avalanche Rider's over Fulminator Mage's?
For run reason, they are nine dollars cheaper. Through play testing I've found that Haste is actually relevant and being able to blow up basic lands is helpful against decks such as Martyr or MBC.
What's with the Manlands and Kessig Wolf Run?
In really grindy games versus Gifts, UWR, or Grixis Control, it's highly possible that they have countered all of your Living Ends. The manlands give you a little bit of extra reach by allowing you to get damage in.
Faerie Macabre?
You can discard Faerie Macabre in response to a cascaded Living End. Use this to exile pesky creatures in their graveyard. Really useful in pre-board matchups versus Gifts.
Beast Within?
Beast Within ends up being a cath-all clause in game one versus alot of decks. It can snag a particularly nasty Liliana or deny your opponent a vital color. I like to target lands that produce U!
The sideboard is purely meta game based.
Beast Within - Extra Hate
Brindle Boar - Jund / Zoo Matchup
Duress - Combo or Counterspells
Faerie Macabre - Takes out their big threats in the bin
Ingot Chewer - Affinity
Krosan Grip - For decks running RIP, Tormod's Crypt or Leyline of the Void
Pithing Needle - Planeswalkers or Deathrite Shaman
Ricochet Trap - Counterspells