Part 3! I feel SO lost, but at least I have loot.
Let me give you a little hint for the puzzle with 2 dice-like shapes. You've been in a room with a big shining face and pillars. Small faces resemble the buttons. Big faces resemble that the whole room is a solution. Maybe pillars are the hint or maybe torches. Who knows? There was a big face in the first dungeon too. But you've been there so much time ago that you might've forgotten about it. Hints for the puzzles are always located on the same floor by the way. This should help you to get the legendary loot on the optional path and beat the whole dungeon without breaking a sweat ;)
I made this guide yesterday. Perhaps you'll find it useful.
https://steamcommunity.com/sharedfiles/filedetails/?id=1848450088