To release the sasquatch: on the Left side of Icewind Path, there is a frozen cave. If you unleash a meteor onto it, it will allow you to purchase Sasquatch. Other than the achievement, I don't recommend it. He has a lot of health, but that's about it.
Oh, come now! People, Stop asking for upgrades and stuff! This game is not meant to upgrade your game. It's to upgrade your skill! Hah! I couldn't even get past 2 when I first started. Now, Im getting real far!
Love this game. It's hard to find great launcher games with so many out there, but this one is unique in that it doesn't just rely on luck, but also on skill.