1) Fungal Mages are a monster in the Polypore Dungeon, an area released not too long ago where all the creatures are weak to magic and have high resistance to range/melee. 2) No quest is needed to access them, you can run from the duel arena, though if you have unlocked fairy rings then code B-I-P will put you at the entrance. 3+4) I don't know about the slayer xp, but they drop noted herblore secondaries pretty often. If you sprinkle neem oil on them their attack speed and damage is reduced making them easier to kill without too much food. 5)A good setup is to use ahrims and a polypore staff, a very good weapon with its own spell that doesn't need runes to cast. 6)A cannon doesn't have reduced damage like other ranged weapons, but if you use one you will be attacked by non-sprinkled monsters, and they will do a lot of damage. Your choice whether to use one or not. The fungal mages drop accursed ashes when they die, so one infernal urn should be able to last you the whole task. Hope this helps!