White Wolf's World of Darkness is probably best known for its various supernatural lines that allow players to create characters that are part of the shadowy modern world. Whether vampires, werewolves, mages, changels or prometheans; each of these supernatural creatures have their own goals, power structures and enemies. But since these different lines are similar at its most basic there is a desire, often from players, to run crossover games.
In a world inhabited by the weird and deadly it should stand to reason that at some point these supernatural creatures will cross each other's paths. Unlike the previous version of the World of Darkness (Vampire: The Masquerade, Werewolf: The Apocalypse, Mage: The Ascension, etc.) the supernatural denizens of the 'new' world of darkness are not necessarily antagonistic towards one another. Their spheres rarely cross and even when they are rarely at cross-purposes.
But can it work? The obvious problem most storytellers and players will latch onto immediately is the vampire question. All the other creatures can function during the day – vampires can not. Savvy troupes will just suggest that the characters maintain their day jobs to some degree leaving only the evenings to deal with 'other' things. It does not really solve the problem of staying up each night till almost dawn, but it is one explanation.
The vampiric weakness aside there are other concerns that may make a crossover game difficult. Many of the difficulties depend mostly on which two spheres you want to bring together.
Mages and werewolves are probably the easiest to reconcile. Both are still mostly human and can interact with the spirit world (werewolves by virtue of their nature and mages through the Spirit Arcanum). It would require that the game focus primarily on spirits and the spirit world but with a mage or two helping the pack, werewolves may find they are able to take on much stronger enemies than before. By the same token mages are rather squishy and having a big furry tank keeping the abyssal creatures off of you can always come in handy.
Actually mages tend to slot in well with any of the other supernaturals by virtue of their adaptability. The Arcana allow mages to do pretty much anything that put their mind and knowledge to. Mages can head into the Hedge with changels (but need their help to get out again unless they have a key), they can travel into the spirit world (with the Spirit Arcana) and they can even defend them against the Disquiet caused by prometheans with the right Arcana (Mind and Prime).
Oddly changelings and vampires can also get along rather well. Both games have political elements (covenants and the courts) and both creatures are trying to hold onto some semblance of humanity. The sunlight issue is still a problem and vampires have no way to enter or leave the Hedge. After this, they can be a potent combination with a combination of politicking, pacts, oneiromancy and emotional and mental control.
The odd ones out, as befits the very theme of their game, are the prometheans. The Wasteland and Disquiet are two very big obstacles that make working with others and staying in one place for a long time difficult. As mentioned earlier mages can alleviate the problem of Disquiet but the others have no such defences. Prometheans also need to be on the move the whole time to lead their Wasteland ruin the environment – a definite conflict point for eco-minded werewolves. To add prometheans to the mix the storyteller may have to make some changes to the rules to help everyone play together a bit better.
As the rules stand crossover games are certainly possible. The problem, however, lies in reconciling some of the obvious differences between the different supernatural 'races'. Mage is perhaps the easiest game to incorporate into the others. To really incorporate the different lines some changes to the rules may be necessary to lessen the impact of various weaknesses or bonuses. White Wolf has broached the subject of crossover games in some of their books but here are some suggestions from my own experiences:
- Vampires still take damage from sunlight but can stay awake during the day (inside) by spending additional Vitae. They are a bit sluggish though and receive a -1 penalty to all Finesse based rolls.
- Supernatural creatures add their supernatural advantage to resist Disquiet and also get over the effects twice as fast as mortals.
- Changelings can make a pact with a +3 boon called 'Hedgewalker' that allows a supernatural creature the ability to enter and leave the Hedge by spending Willpower and their power source (Essence, Mana, etc.) and rolling Wits + Occult (this is after they have found a way out). Also remember to check the sourcebooks for more rules relating crossover games. The Promethean sourcebook Strange Alchemies has rules relating mages and Disquiet, for example.
At the end of the day the success of a crossover game depends entirely on the troupe. Some characters are going to have to make sacrifices and some rules may have to be bent and changed, but it can be done. Just remember the cardinal rule: as long as it makes for a good story, go ahead and do it.