The participating regions in Europe include the UK, Ireland, Portugal, Germany, Spain, Italy, Norway, Sweden, Finland, and Switzerland
Honestly this border hurts my eyes just to look at, though admittedly I havent been able to see them in person but the design that has been shown by Wizards of the Coast online is just painful to look at
Wing and Claw was the first deck that was viable to use for the event and constructed runs, where you pay either a certain amount of gold or gems (the currency you can buy with physical money) and you get to participate in the event
It should be noted that Sealed is generally slower than Draft and expensive cards will usually have more of a home there
For those brimming with questions, head to DailyMTG, where Gavin Verhey has a comprehensive article about Archenemy in Duskmourn: House of Horror
How about a mill combo