The Ur-Dragon is potentially the most powerful Dragon commander with its 'eminence' ability making the rest of your Dragons one generic mana less to cast, even if The Ur-Dragon isn't on the battlefield
If you are tempted again, nothing happens
With such weird cards being printed, Wizards of the Coast has had to find ways to make sure people don't accidentally put a card with Denimwalk (can't be blocked by a player wearing denim) or Art Menace (can only be blocked by creatures with two or more characters in their art) into their normal Magic decks
Whenever an instant or sorcery card leaves your graveyard, put a +1/+1 counter on Murktide Regent." Even if all you do is cast two of these in a row, you'll suddenly have a 13/13 and an 8/8 dragon if every exiled card was an instant or a sorcery
Houndooms second attack, Snarl, has a neat effect, causing your opponents next attack to deal 100 less damage