Legends are historic, after all
If Kozilek is countered or otherwise leaves the stack in response to that triggered ability, the triggered ability will resolve as normal
It's easy to forget just how many Magic players are relatively new to the game (and likely even a larger percentage of casual players, since many players start playing casually before moving on to more competitive play)
Overlord of the Hauntwoods Discussed above, but I see this as one of the most powerful cards in the set that will potentially play a role in a wide range of decks both existing and new
Either way, Grakmaw, Skyclave Ravager will find its way into any Golgari or Abzan decks this season, especially those that care about counters
Planeswalkers who happen to also be Dragons will also not be discounted, unfortunately, but will still be included in the deck because of the Ur-Dragons other ability, being permanents