I have played Werewolf exactly once, for a one-shot convention game (and we were all Kinfolk, trying to be heroic when the big furry guys were unavailable…). It was fun, but I don’t really have a lot to say about Werewolf. (Some werewolves did show up in Heart of Darkness, though. Sarah was in charge of that part. It was… interesting. Educational for all involved. Everyone survived. We counted that as a win. It also goes to prove that if you’re running from the Black Hand, there are in fact a FEW places they will NOT follow you into—and Garou territory is one of them.)
Normally, I’m not that keen on crossover. It can work (and it did), but you have to be careful to make sure relative ‘power’ levels are balanced (in terms of STORY, not necessarily in terms of a fight – unless a fight is what the story is about). Werewolves make good (actually, pretty damned deadly) adversaries for a vampire story (and vice-verso). But there’s one part of the whole Garou setting and mythos that we did import over to Vampire, and it worked very well, especially with these particular characters.
That was the whole concept of the spirit world, which overlapped nicely into Spirit Thaumaturgy.
This all started when Sarah and I decided to introduce her already-established character Etienne de Vaillant into the same setting Myranda and I were using. In the chronicle he’d come from, Spirit thaumaturgy was Etienne’s specialty, and the study of spirit thaumaturgy was RARE among Tremere because most Tremere just couldn’t see or sense spirits, and therefore had trouble believing they really existed. (Demons, yes. Nature spirits, no). And the reason Etienne could see and interact with spirits when most Tremere could not was that he was Kinfolk, and had some early experiences with some tolerant Garou. Etienne was somewhat of a pioneer in the art of combining Tremere blood-sorcery with Spirit thaumaturgy, in fact—he literally wrote the book on it (The Spirit Mirror, still used by the handful of Tremere who follow this path as one of their basic primers).
So, since that was pre-established background, we kept it—and while we were at it, adapted chunks of Garou spirit-lore as ‘canon’ too. We’ve continued to adapt and refine the concepts over the years. (we also fudged the actual levels of Spirit Thaumaturgy).
Spirit thaumaturgy does tend to rely on less hermetic approaches to magic and concepts of how the unseen universe is put together, so the number of Tremere who have the talent and ability for it are few. But Tzimisce kolduns see a much more animist universe, and so they are much more likely to use spirits in their workings, and account for their presence when designing wards. Physical boundaries do not affect spirits—but magical ones do, such as wards and circles.
Spirits can be called up/summoned via thaumaturgical rituals, or if already present, spoken to or negotiated with. (Negotiation is more time consuming than binding, but you can often get more cooperation—bound spirits will obey, but rarely ever go beyond the exact limits the binding imposes.)
There are many kinds of spirits: elemental spirits (water, earth, wind, fire, etc.); loci spirits (tied to a particular place or item); and “conceptual” spirits. Conceptual spirits are the broadest type—they’re personifications of strongly held beliefs, cultural icons, or things ‘everybody knows’. Animal spirits personify the traits of the animal, both its ‘natural’ traits but also those assigned it by folklore (ie, the fox as a trickster, the horse as a symbol of swift travel). Other such spirits might include ones from folklore (boogieman, Thing Under The Bed, guardian angel, Blue Lady, etc.), or personifications of a trait (a spirit of gluttony, avarice, or lust). Bane spirits are conceptual spirits too—personifications of anger, grief, pain, death, terror—that feed on those emotions.
The Garou theurges will tell you that the only spirits a vampire magus can summon or control are bane spirits. Some vampire sorcerers (including Etienne) dispute this. But then, the Garou don’t differentiate much between vampires, either—one undead blood-sucking leech is much like another undead blood-sucking leech to them. So it could be that any spirit associated with a vampire spirit-magus just picks up the same undead reek by proximity—especially if the spirit is ‘fed’ by means of the vampire’s own blood. So perhaps even the lore of the theurges should be taken with just a bit of sea-salt….
Mixing the Garou spirit-world in with the Vampire-centered World of Darkness does make for some interesting storylines though…. (and bringing in Garou who weren’t quite of the “kill it first and then divine its intentions from the ashes of its entrails” school of thought was interesting too!)