The 
Ancient Compass is a compass from the Deeper and Darker mod that points to the nearest Ancient Temple once you’re in the Otherside. You’ll craft it from a normal 
Compass and four 
Warden Carapace, so it’s something you’ll be able to make after your first few trips into an Ancient City.
Ancient Temples hold the 
Sculk Transmitter, the Catalysis enchantment and most of the Otherside’s best loot, but they’re hidden underground and easy to walk right past. The compass takes care of that, and it’s the quickest way to find a temple without digging around blindly.
Crafting
Place a Compass in the middle of a 
Crafting Table and put a Warden Carapace above, below and to either side of it. The corners stay empty, and you’ll get a single Ancient Compass back.
Warden Carapace comes from killing the Warden and from the Chests in Ancient Cities, so you’ll usually have a few spare by the time you’ve opened the Otherside Portal. It’s worth making the compass before your first trip through, since the temples are where most of the Otherside’s progression happens.
How It Works
The first time the compass is in your inventory while you’re in the Otherside, it’ll search for the nearest Ancient Temple and lock onto it for good. From then on the needle points to that temple, so you can follow it the same way you’d follow a normal compass to spawn.
It works much like an Explorer Map does, as each new compass picks a temple that no other compass has been pointed to yet. That means a fresh one will lead you somewhere new once you’ve cleared out the first, which is handy when you’re hunting for a temple that has a secret room.
The needle only points while you’re in the Otherside, and it’ll spin like a normal compass does in the Nether anywhere else. A compass that couldn’t find any temple nearby will keep spinning as well, so crafting a new one further away is the fix.
Since it only locks on once, it doesn’t matter where you craft it, as long as you carry it through the portal afterward. Keeping it in a Chest won’t do anything, though, as it has to be in your own inventory in the Otherside before it’ll search for anything.
Version
The Ancient Compass was added in 1.4, so it isn’t in the 1.20.1 version of the mod, which stops at 1.3.3. On that version you’ll have to find temples by exploring, and since they only generate in the Deeplands, low down near the bottom of the Otherside, it’s worth searching there first.
If you’re playing a modpack, it’s worth checking which version of Deeper and Darker it uses before looking for the recipe. A pack on 1.21.1 will usually have it, while most 1.20.1 packs won’t, even though the rest of the mod works much the same way.
FAQ
Put a Compass in the middle of a Crafting Table, with a Warden Carapace above, below and on either side of it. Warden Carapace drops from the Warden and can also be found in Ancient City Chests.
It points to the nearest Ancient Temple in the Otherside, which is where you’ll find the Sculk Transmitter and most of the dimension’s best loot. It locks onto that temple the first time you carry it in the Otherside.
The needle only works in the Otherside, so it’ll spin anywhere else, the same way a normal compass spins in the Nether. If it’s spinning in the Otherside too, it couldn’t find a temple nearby, and crafting another one somewhere else will usually fix it.
It was added in 1.4, which is only available for 1.21.1, so the 1.20.1 version of the mod doesn’t have it. On 1.20.1 you’ll need to search the Deeplands by hand instead, as that’s the only biome where Ancient Temples generate.
