I am very new to the game, but trying to make up ground. As I have looked at lists and strategies, I see players playing actively with content that has not been released to the general public yet. Most notable among wave 8 upgrades is the Thread Tracers. My question, simply, is how/why is this done? Do some players have access to these sets very early, or is it about knowing it will be released and playing with the "cards" without possessing them to playtest? Curious here as I am sure we are all anxious to use some of them.
Thanks