So I beat the seeing one boss in the temple and have four cards. However, I'm not sure how to progress. By the portal after the boss, there's a green statue blocking the way that "isn't going to move soon", and now that I have the four cards I can explore the loop in the upper left of the second outside area (outside the temple), but there isn't anything there but a bunch of enemies. I've explored those three areas again, but can't find anything. I feel like I'm probably not getting some function or action in the game because I know this is early on...
The gates you open with cards lead to health upgrades.
Otherwise, I believe what you have to do is acquire the boots, if you haven't already. It has something to do with the cat that follows you in the lake area. Bring him to the orange fish looking guy to the east.
It's just after the first boss (in the temple). I haven't gotten to a lake yet. Nothing new besides that gate seems available. There is a spot with a statue stuck in the path after the boss near the portal, and some areas to the right outside the temple (another exit, but it's blocked by trees)