Angolmois is malevolent substance featured in Little Witch Academia Tetralogy: Ragnarok.
Also known as Nidhogg's essence or Blood of Nidhogg (in its liquid form), this hazardous and corruptive magic energy that both emanation and remnants of all-powerful cosmic serpent itself as well as dark half of Pomokai Holoholonas. Unlike other forms of magic energy, angolmois is very volatile and hazardous that it can corrupt the mind of witches who infected/channeled it and mutated her body.
This substance is Naglfar's primary target for their Ragnarok plan: Due to all salvaged remains of Nidhogg lacked enough Angolmois to properly reassemble the cosmic serpent as Nine Olde Witches had combined it with Yggdrasil's essence which resulting the birth of Pomokai Holoholona races, Acolytes of Nidhoggr begin to capture and experimenting on those magical creatures so they can extract angolmois from their bodies. However, due to the Acolytes' aggressive approach, they drawn the attentiom from Witch Community and subsequently massacred. Even so, Croix and Naglfar managed to continue their work under Witch Community's radar and more succcessful due to Croix's careful planning and more sophisticated methods.