<(WARNING EARTHDAWN REFERENCE ALERT! CODE VIOLET!)>
The Enemy is the ancient Horrors that arrive when the mana level reaches a certain point and then disappear when the mana level drops. They come in many forms from a pure astral spirit form to an Awakened dual-natured form. Their entire purpose is ravenous destruction, consumption and corruption. They feed in several ways, by eating matter ravenously. These physical Horrors will eat anything: gemstones, rocks, grass, fertile soil, animals, people, anything. There are other more dangerous Horrors that feed on negative background count and living Karma. These forms are more powerful because the Karma they steal allows them to grow. Simultaneously, the karma they acquire by stealing from other beings additionally imprints them with the personality quirks of the people they steal it from.
This brings me to Yrsgr'athe (pronounced Ears-Grr-Ayth, I believe) He is one of these higher form Horrors. Originally, it simply drained its victims, however, as it grew it took on a name and a form and then formed a Modus Operandi for how it behaved. "He" takes the form of a hooded skeletal figure, when manifest, of course. He will find someone proud and vainglorious and offer them strength, in a sort of Pact (nearly identical to the Pact made between Shadow Spirit and a Corrupted Magician) and give them additional Karma pool and power. However, he will use this link to slowly corrupt the the bonded and then at the right moment, he will betray them, using the emotional upheaval caused by the fall of the victim to drain all the energy and karma from the target. He prefers to drain strong and powerful people as they put up a greater bit of amusement and can take what he dishes out to them as the situations he places them in get more hectic and desperate, earning more karma for him to drain in the end. He originally never derived pleasure from any of this, but as he preys on metahumanity, he becomes more and more like them, emotional and affected. The pact that he uses would only work on a type of magic user. which would explain why the magical personnel was pulled from Crater Lake.
Horrors have a nasty effect on the area around them, in particular, astral space. They create a mana warp around them, twisting the mana in a horrible and disturbing way. Their simple presence creates a horrible background count which makes magic use very dangerous without filtering metamagic. Also, Horrors have the ability to "mark" their targets. They essentially "implant" an astral link inside the aura of another being which allows them to affect them with sorcery without actually having a material link. Treat this as if the linking test in a ritual sorcery test succeeds automatically.
If you were to use Yrsgr'athe in Shadowrun, he'd most likely be considered a powerful Free Shadow Spirit, who will make a Pact with a character in exchange for Potency. He has the Karma Drain ability that he will use when he pulls his potency from the bonded in a situation where the victim desperately needs it. If the players encounter Yrsgr'athe, they will probably die unless the Horror is weak in a low mana level of some sort.
