Ectoplasm

Ironman verdict

At least 9 monsters drop it. The easiest is Cockroach drone (level 4, 1/1,398,101.33); the best rate is Seren spirit, at 1/512, about one every 2 kills. You can also make it yourself: it takes 40 Necromancy and gives 310 Necromancy XP, using Bucket of powerful slime, 2 × Elemental I, Change I, Commune I and 4 × Basic ritual candle. There are 2 other recipes below. Other sources include Ice troll grunt, Ice troll female, Bork and Bandit (Wilderness), plus 4 more listed below. Making ten takes 10 × Bucket of powerful slime, 20 × Elemental I, 10 × Change I, 10 × Commune I and 40 × Basic ritual candle and gives 3,100 Necromancy XP. Reaching level 40 Necromancy takes 37,224 XP in total; the Necromancy calculator counts the actions and materials to any target, and the Necromancy guide has the Ironman training route. 12 recipes use Ectoplasm, including Attraction I, Attraction II and Attraction III. Ectoplasm is available on free-to-play worlds too. It is tradeable on normal accounts, but an Ironman cannot use the Grand Exchange or trade for it, so the sources on this page are the whole list. High Alchemy turns one into 6 coins, which is 4 less than the shop price, so buying it to alch does not pay.