General Method Description

Aberrant spectres are one of the very best money monsters in the game. They drop tons of herbs, along with high-level herb seeds and the occasional rune full helm or even dark mystic top. They are fairly tough monsters because of their relentless magic attack, which does significant damage even with high levels. But since you need to bank frequently anyway due to all the herb drops, it's easy enough to fight them with cheap food.

The original location of the spectres is the Canifis Slayer Tower, but if you complete the quest Smoking Kills and earn the right to make a Slayer helmet, you can fight them instead in the Deser Slayer Dungeon in Pollnivneach. This is recommended because there are far more spectres in this location, so you don't have to deal with all the competition from other players that occurs in the tower.

With monsters that drop a large number of herbs, there are trade-offs between keeping all the herbs or leaving the lower-valued ones so you can try to get more of the ones that cost more. There is also a trade-off between using a beast of burden to get more herbs per trip, or summoning a macaw for its herb enhancing benefit, because the macaw increases the percentage of good herbs (ranarr and above) by a hefty 40%. The key factors that determine the best approach are the number of herbs you get per hour from the monster, the distance to the bank (and thus how much time you waste per hour banking if you take more trips) and the value of non-herb drops.

Aberrant spectres drop very large numbers of herbs, but also drop many other valuable items. They are, in effect, close to a bank, because you can get to them fast using a ring of slaying. In my tests, the best approach is to use a macaw familiar for its herb quality enhancement, and keep only guams and herbs harralander and above (that is, everything but marrentills and tarromins).