You'll probably have to face a couple headless brutes in the catacombs, and one always seems to spawn in this room. If you've been to Custard Mansion, then the brutes should look familiar, but the version here is easier to kill because it has fewer hit points. Backing up while pinging the brutes with ranged attacks doesn't work very well since the brutes are surprisingly fast, so you might have to go toe-to-toe with them and take your lumps.
2 - Secret Door
The loose brick that opens the secret door is located just to the south. Inside you'll have to fight off a few ghouls and mummies, but you'll find a coffin and a level 4 chest. A scout skill of 2 is enough to detect the loose brick (if the loose brick needs to be detected at all).
3 - Secret Door
The loose brick that opens the secret door is located just to the south. A scout skill of 2 is enough to detect the loose brick (if the loose brick needs to be detected at all).
4 - Galdryn's Horn
Galdryn's Horn is your objective in the catacombs. You won't be able to take it until you've talked to the magic mouth (#5) and dealt with the guardian beast (#6).
Note: If you're playing version 1.4/1.5, then you'll find that Galdryn's Horn is a trinket that you can wear (and a good one, too). In earlier versions, you'll only find the horn under the "invoke" section of your inventory. In MMXII the horn is once again unwearable, but you can still invoke it by placing it in your hotkey bar and activating it from there.
5 - Magic Mouth
The magic mouth controls the cage surrounding Galdryn's Horn (#4). It won't remove the cage until you've spoken the magic password. You'll get the password when you kill the guardian beast (#6). Then the password should become a dialogue option when you talk to the magic mouth.
6 - Guardian Beast
The guardian beast looks like a minotaur. It does not hit very hard, but it has an annoying breath attack that will prevent you from doing anything other than moving. Since the beast also doesn't have a huge number of hit points, you can either ping it with ranged attacks while avoiding its breath, or you can move in for melee attacks and then run away when it breathes on you. If you have a lot of problems with the beast, then you can let it chase you to the ladder (Exit E). Enemies can't climb ladders, so if you climb up then you'll be able to hit the beast with ranged attacks without having to deal with its attacks.
When the guardian beast dies, the words "Espiritus Caldere" will appear in the air over it. That's the password you'll need for the magic mouth (#5).