Brine rats are Slayer monsters that require the partial completion of Olaf's Quest to be reached or assigned as a slayer target. A Slayer level of 47 is required to fight the brine rat. They are located in the Brine Rat Cavern, which requires a spade to gain entrance. Brine rats have relatively low defence, but they can deal over 100 damage, relatively high for their combat level. The Brine rat also doesn't hit as accurately as the Bloodveld and Infernal mage, so collecting death and blood runes is easier.
Brine rats are usually neglected, similar to the Infernal Mage, since their drops don't earn a lot of profit. They drop a fair number of runes and are much easier to defeat if you're looking for death and blood runes.
Multiple safespots exist, one of them involving the use of the light coloured skeleton in the room. Rangers and Mages may attack across these bones, trapping the monsters on the other side of the pile.
If you bring a tinderbox and logs, you can cook their meat or the raw shark drops to last longer if you are doing slayer. Alternatively, there is a fire tended by Olaf Hradson located just outside of the cavern's exit which provides an excellent location to cook either the rat meat or dropped raw fish. They also drop the brine sabre.
If you take the raw unnoted fish, you can leave the cave and cook them using the fire next to Olaf. This way you will not have to bank as often, but you will need to have at least 80 cooking to do this. You can also take a stack of logs with you and cook them at the spot.
You can also bring bones to peaches tabs. All you have to do is pick up the bones and click on the tab for an unlimited supply of peaches.
It is advisable to bring a Bunyip (level 68) pouch and some scrolls. Brine rats drop plenty of raw fish with which you can heal yourself by using the bunyip's scroll, "Swallow Whole", to keep your life points up. Not recommended if you have very high combat stats though.
Do not forget to bring a spade. Spade on the tool belt does not count! (A spade respawns next to Olaf)
Bring armour with good defence as well as a good weapon. Higher levels will not require as much food, however, they can cook the raw food drops of the brine rat.
You no longer need to finish Olaf's Quest in order for the Brine rats to drop the Brine Sabre!
Brine rats are considered to be a very good source of money for their noted drops and the much coveted brine sabre. However, the brine sabre has been dropping in price.