When you complete all astrariums in a map, a secret cave/dungeon/room will open. It will also be indicated on the map.
Usually you get some unique item from the chest you loot in that cave.
Below will show you what you get from completing all astrariums in the map. It’s good to note since you might be overleved when you decide to complete the astarium puzzles at a later time.
The Hinterlands Astrarium Reward
- Snake Blade dagger, level 9 requirement.
Crestwood Astrarium Reward
- Superb Belt of Fire Resistance
The Storm Coast Astrarium Rewards
- Band of Red Crossing level 8 unique bow
- Free Marches Banner Crown
- Dreamweaver Staff
The Western Approach Astrarium Rewards
- Masterwork Enchanter Mail level 9 unique light armor.
- A Superb fire rune schematic is also located in the cave.
Emerald Graves Astrarium Rewards
Contains 2 other chests and a main chest.
- Deathward level 11 unique staff.
- The other chests may contain tier 3 schematics.