It just has such a convenient split of damage for such a low low cost
Factions were well balanced, there were a variety of new and/or powerful cards you could open within factions, and many people of all skill levels took to it quickly since you could just jump right into a game without spending time deckbuilding
It also grants you protection from everything until your next turn when it enters the battlefield, which makes it a good target for blink effects that can trigger that multiple times
Nyx Fun: 2 Impact: 3 Chaos: 2 Some decks will love this, some will hate it and the player who has been burned one too many times by stax-like prison decks and is packing all the enchantment removal will finally have their day
And finally, we have retreat cost
Chatterfang, Strategist Emeritus, or Chatterfang, Chittering Mentor, or something along those lines