As you wander the world of Tunic, you will surely run into puzzles along the way. One of the earliest ones you can encounter is these large sealed doors.
How to open the sealed doors
A large part of Tunic is discovering things for yourself, including these large doors covered in markings. Thankfully, you can easily get them to open for you and take the treasure within. You can open these doors by interacting with them, and then drawing the pattern on the door with either your d-pad or arrow keys. Following this line perfectly will cause the doors to open, allowing you to enter.
In some cases you will need to enter the code on the side of the door, however, it is not always clear as to which code you should enter. When available, trying all patterns on the door is a sure way to make it open. You will also be able to find this tip on page 43 of the instruction manual.
For more on Tunic, be sure to check out Can you translate the language in Tunic? or What do fruits do in Tunic? here on Pro Game Guides.