One possible fanfiction could be about War and Uriel teaming up to face a new, unknown threat in the Darksiders universe. Maybe a powerful demon that has emerged from a previously sealed realm, and they have to combine their unique abilities to defeat it.
One possible scenario in such a fanfiction could be that War and Uriel start off as reluctant allies. War, being the Horseman, is initially focused on his own mission. But as they face various challenges together, they begin to notice the strength and determination in each other. Uriel is impressed by War's unwavering resolve, and War starts to see Uriel's more compassionate side beneath her tough exterior. Their relationship could develop gradually, with small moments of shared understanding and mutual respect, eventually leading to a deep romantic connection.
Perhaps there is a dark force corrupting the angels, and Uriel is suspected of being influenced. War is sent to investigate. As he gets closer to Uriel, he realizes she is innocent but they must work together to find the true source of the corruption and stop it before it spreads throughout the entire angelic realm. This would involve a lot of action and tense moments as they fight against both the corrupted angels and the real threat behind it.
Another interesting concept for a Darksiders War crossover fanfiction could be a crossover with the Diablo series. Imagine the dark and gritty world of Diablo mixing with the post - apocalyptic world of Darksiders. The heroes from Darksiders could be lured into the world of Sanctuary in Diablo, where they have to deal with the hordes of demons while also trying to find a way back home.
It has a moderately close connection. Some key elements and storylines are retained, but there are also some variations to make it suitable for different mediums.
In a War and Uriel romance fanfiction, the element of forbidden love could be significant. Their different allegiances, War being part of the apocalyptic forces and Uriel an angel, make their relationship something that would be frowned upon by many in their respective worlds. This can lead to secrecy and the added excitement of being discovered. Their shared experiences in battles and facing common enemies is also crucial. These shared moments of danger and survival can strengthen their bond, as they rely on each other's skills and abilities. And finally, the exploration of their individual backstories, how they became who they are, can give depth to their relationship as they understand each other better through these revelations.
If you're doing a crossover with the Mass Effect series, Shepard could be a great character to include. Shepard's leadership and combat experience against various alien races would be interesting when paired with the Horsemen's fight against the forces of Hell. Also, including some of the alien species from Mass Effect like the Krogan or the Asari could create some really cool interactions.