Ectoplasm is an alchemy ingredient in The Witcher that is obtained from the bodies of ifrits, barghests, specters, noonwraiths, and nightwraiths.

Source

• In Chapter I, an old townswoman will tell Geralt about Barghests in exchange for food. While the conversation does not result in a Bestiary entry for barghests, it does result in an ingredient entry for Ectoplasm.
• Barghests
• Physiologus
• Specters, Wraiths, and the Damned
• The Last Wish

Notes

• Geralt can loot the remains of barghests in Chapter I for ectoplasm without having journal entries for barghests or ectoplasm.
• Get as much as you need in Chapter I, because it becomes a rather rare ingredient in the Chapters II and III.