Note: Lanterns aren't part of a puzzle, they can be placed around to help illuminate areas.
Obelisk sides: Up faces mausoleum, down faces graveyard entrance.

Stone buttons
Hint 1: Explore the environment for clues. Is there three of anything else?
Hint 2: A note can be found near the right corner of the fenced area next to the mausoleum.
Solution: Right, left, middle (Stone stands ordered shortest to tallest).
Result: Stone stopper for the slab above the buttons lowers, allowing it to be moved.

Stone slabs
Hint: There are slabs around the obelisk that can be interacted with.
Slab 1: On left side of obelisk at around eye level. Slide down to reveal rune and dislodge obelisk side. Dislodged slab reveals a shovel.
Slab 2: Right side, can be moved after solving stone buttons puzzle. Slide right to reveal rune.

Key to graves
Hint: Solving the above puzzles, and illuminating the obelisk can help find it.
Solution: The key (+ a rune) is hidden on the back of Slab 2.
Result: Access to pumpkin and note, as well as closer look at graves.

Runes
Hint 1: There are 4 runes hidden around the obelisk and area, and sliding blocks with runes on the north and south sides of the obelisk.
Hint 2: Three are found on the obelisk involving stone slabs, the other is found on the book.
Solution: (Counting from 0) slide the north side upper block to position 2, lower block to position 3. Slide the south side upper block to position 3, and the lower block to position 2.
Result: Compartment opens with a locked chest.

Key to locked chest
Solution 1: The fence to the graves without the locked gate can be pushed over.
Solution 2: Use the shovel to dig at the grave, revealing a key.

Code
Hint 1: A piece of paper can be found relating to the code.
Hint 2: The paper shows the four graves and candles.
Solution 1: Count the number of candles at each grave from left to right on the paper.
Solution 2: 2144

Activating the obelisk
Solution 1: Check the book with all objectives ticked, interact to cause a slab to glow.
Solution 2: Slide the glowing slab out of the way, and press the stone button inside.
Result: This powers up the obelisk and completes the room!