Hellhounds are mid to high level demons often given as a Slayer assignment to mid to high level players. The introduction of the Summoning skill brought about a rise in players killing them due to their gold charm drop rate. They have the third highest combat level of any monster outside of Daemonheim in F2P, surpassed by the deadly red spider and revenant knight. Hellhounds may also be purchased to guard a player's dungeon in the Construction skill (see Hellhound (POH)).
Hellhounds can be an excellent way to train melee for F2P players, as players can exploit their weakness to slash with the Rune 2h sword and Gravite 2h sword, possibly getting more experience per hour than Deadly red spiders. Keep in mind: hellhounds are found only in the Wilderness in F2P worlds, so beware of the risk of PKers. The area is usually uncrowded.
God Wars Dungeon (m) Note: Although the hellhounds here give significantly more slayer experience, there are very few of them in the dungeon, including only one inside Zamorak's fortress, making this an inefficient training option.
They also don't count when assigned a "dog" slayer task.
Hellhounds could be dogs or wolves that were corrupted by magic or something they ate (similar to the origin of hellcats), rather than actual demons. This would explain why they drop bones.
On 16 June2009, hellhounds were placed in the wilderness volcano, making it the first P2P monster to enter F2P. It also broke the record of strongest, non-revenant, free to play monster with a combat level of 122.
After the ring of wealth update on March 162011, the charm drop rates of hellhounds and rock lobsters had "gone walkabouts". This caused hellhounds to drop gold charms less frequently. Rather, they seemed to drop blue charms much more often. This was, however, fixed on March 28 as noted in the patch notes of that date.