In the tall thin level (can't remember the number) there's a secret passage along one of the walls. Just crawl into the walls and you'll find it. In the secret room you'll find four goblins.
sirkaid
Recent community posts
You only need one turret for most of the game since it's basically impossible to kill the enemy until 6 minutes on or so. The strat is to always upgrade the bed when possible, then upgrade the door if you can't upgrade the bed, then upgrade the turret if you can't upgrade the door. Once you get to 5 minutes in you should have a powerful enough economy to fill up the rest of your slots with turrets and go ham.
Focus on upgrading the bed whenever possible. Turrets are only useful in the late game - you're never going to be killing the monster until at best six minutes in, so having a lot of turrets is kind of irrelevant up until that point. Upgrading the door gives it a full repair, so don't manually repair it unless you don't have the money for an upgrade.