Fairly simple concept; slayer tasks you can optionally do at a spot where using multi target spells is the optimal thing to do. It would directly give chaotic staff more of a use and would sink an absolute ton of blood/death runes. I would also enjoy having to gear up differently for a change.
The general idea is that whatever monsters that are picked for this are in a spot where there are a large amounts of spawns quite close to one another in a multi area with a decent respawn rate. These monsters have to be aggressive so that they clump together. This means you can constantly barrage and consistently hit multiple targets. It's good slayer exp, it's good magic exp, the drawback is that it's expensive in terms of runes.
Some monsters I would recommend for this are:
- Dagannoths
- Nechryaels
- Dust/smoke devils
- Abyssal demons
This could also be done to spiritual creatures, but they generally need better spawns.