Cards from special guest set?

[Berserkr]

I just got a Sylvan Tutor from the new alchemy packs, was really surprised to see it reprinted then got looking and saw it's from a set special guests, so I looked just at that set, besides crafting these is it just a rare chance to get them in other packs?

[Winter Wolf]

Yeah special guests are one of the bonus curated lines you can obtain in packs. They are all mythics as far as I recall (thus show up fairly rarely). There's a list of what packs have them afaik on wizards site somewhere.