Once you've made it to the greenhouse in Ravenlok, you'll find that you can't enter it initially. There is a puzzle to solve to gt you access, here's how to do it.
Directly outside of the greenhouse, there are two large statues, each one has two animal icons on the front of them. To solve the greenhouse puzzle and to get access to the greenhouse, you have to search the surrounding area for animal statues that match the animal depicted on the two statues that are outside of the greenhouse and enter those numbers on the statues.
Watch out, that you will have to participate in some battles on entering the numbers so make sure you are ready and have enough of any potions that you think you may need.
While on the surface, if you don't know what you are looking for immediately this puzzle can be a little confusing, but once you've worked out that you actually just need to count the corresponding animal statues outside of the greenhouse it's fairly easy.
If the numbers you have tried aren't working, or you just can't be bothered to count all of the different animal statues that are around the greenhouse area, here is the solution to the puzzle. Just enter the following numbers in the correct animal location.
Bear - 2
Rat - 0
Owl - 6
Ram - 4
A lot of the puzzles in Ravenlok are of a similar nature, just try to think a little outside of the box if you are stuck.