Dogs are mobs that can be tamed to follow and fight for their owner. Dogs can be found in the Underworld randomly throughout all levels, and have a chance of spawning from an Altar. To tame a dog after you found one, simply drop raw or cooked meat or fish1 at a time onto the floor around the dog and wait until it walks over to the meat. It will "eat" the meat and say "arf!" which means that you are now a proud owner of a dog!
To command your faithul dog, two simple commands can be issued. They must be done using area chat by either saying "stay" or "come". The words must be written exactly that way.
The command "stay" will make the dog stand where it was told to and wont go after their owner, though they will pace around a small area and can wander off.
The command "come" will make the dog follow you if it was told to stay, which will make the dog teleport to where you are standing.
For the commands to work, the dog must be in the same "screen" as the player. If multiple dogs are present, they will all obey to the same order together.
Dogs wont join fights if they are told to stay.
Dogs can be healed using bandages, and each food item they eat (including dishes from pots) restores 10 points of their health.
Several dogs can follow a player at once.
Training your dog
Beware! You can harm your own dog, always hold a shovel or a bandage, or a repair kit while selecting them.
Dogs can be trained so their stats increase. This is done by letting your dog kill other mobs (any mob works, including animals). Each kill they make grants them 10 max health points more and increased damage as their health increases. At higher health levels it takes more than 1 kill to gain that 10 health. The dog only needs to land the killing blow, so you can help them, especially when they are still weak. The maximum health for a dog is 1000, at which they deal 40 damage per hit on average.
A good place to start is the animals around Galebrook. At around 250-300 health on your dog, take it against snakes, which can be commonly found at Snake Pit and South Sands Desert.
Always bring a bandage to heal your dog, and/or a stack of food. Keep an eye out for hostile players who may want to kill your dog.
When you keep your dog at home, periodicaly check its health, as wolves can spawn on grass and attack your dog if kept next to grass, so it may require healing.