The top four eight (previously announced as 4, now officially 8 as was announced in the Lorecast, possibly more) players from each regional Challenge will earn the qualification for final North American or European Championships events
In Swiss, you get to play lots of games
Oftentimes you could win games my casting the card on your own creature, because youd gain the life & survive another turn
The Uncommon allows players to put up to nine copies of the wraith knight into a deck, which is very powerful in a format like Commander, where players can only have one copy of a card unless otherwise specified
Lutri, the Spellchaser was controversially (and correctly, in my opinion) banned from Commander on release as itd otherwise be an auto-include in any deck playing blue and red (almost any Commander deck fulfills the companion restriction, as this was clearly not designed for Commander)
This encompasses his own melee keyword and a host of other unkeyworded triggered abilities, including Klauth's attack trigger