Horus, the Black Flame Dragon was released in Soul of the Duelist, after much anticipation from the American crowd. This is probably the most powerful of the LV Decks, and it's easily the most broken card in the metagame right now. Horus LV8 has the ability to negate ANY Magic card...for FREE.
However, Horus LV6 is better than Horus LV8. LV6 can be normal summoned through a sacrifice - no big deal. Horus LV8 is a nomi monster, meaning it can ONLY be special summoned through Horus LV6's effect. Note that you don't NEED to use Horus LV6's effect if you don't want to. Horus LV6 is unaffected by any Spell cards, meaning that you can use Dark Hole freely, and the opponent's spells are still useless against it. Horus LV6 is still a VERY strong monster, and Horus LV8 is really for when you're on the offensive and can deal that extra damage without fear.
Since Horus can negate any Magics, then the best way to get rid of him are obviously through Traps and Monster Effects (LV 8 has 3000 attack; sorry, you simply are NOT taking that down). The best counters are Exiled Force, DD Warrior Lady/Assailant, Bottomless Trap Hole, Sakuretsu Armor/Mirror Force, etc. This deck can easily take care of most of its threats.
Mirage Dragon is in because it has amazing protection for Horus when you're on the offensive. No Sakuretsu Armors, Widespread Ruins, or Mirror Forces when Mirage is on the field - and those cards will most likely be the most common forms of Horus destruction. For the same protection while you're on the defensive, Solemn Judgment and My Body as a Shield offer the same type of protection against things like DD Warrior Lady, Exiled Force, or Zaborg the Thunder Monarch.
While Mirage Dragon protects, it does not destroy. Mobius the Frost Monarch and Nobleman of Extermination help to take out Sakuretsus and Widespreads, so that if Mirage isn't around you can still attack freely. Widespread Ruin also has nice synergy with Nobleman of Extermination, allowing you to take out Sakuretsus without fear of removing your own. Treeborn Frog helps with the massive amount of tributes. Also, don't disregard Big Shield Guardna - Dark World will probably be very big this format, and with Nobleman of Crossout back to two, Big Shield can eat Nobleman and Dark World Lightning alive.
Monsters - 19 (8 Tribute, 11 Non Sacrifice)
Magic/Spells - 13
Traps - 8
