A common theme is power. Since Salem is such a powerful figure in RWBY, many fanfictions explore how the male reader either gains power through their relationship with her or is in awe of her power. For example, in some stories, the male reader might learn dark magic from Salem.
There's also 'Salem's New Companion'. In this one, the male reader character is kind of thrust into Salem's world. It explores how he copes with her dark nature and the power dynamics at play. It has some unique takes on the RWBY lore and does a good job of developing the relationship between the two characters.
A lot of these fanfictions also touch on the theme of sacrifice. The reader might have to sacrifice something, like their normal life or relationships, to be with Salem. And there's also the theme of changing fate. Salem is kind of a figure who defies the normal order, and the reader in the fanfic could be part of that process of changing the pre - determined fate, whether it's for good or bad.
You can start by looking on fanfiction websites like Archive of Our Own (AO3). It has a large collection of RWBY fanfics, including those about Salem x Reader. Another option is FanFiction.net. Just use the search function on these sites and type in 'RWBY Salem x Reader' to find relevant stories.
One idea could be that the male pirate reader's ship crashes near Vale. He then meets Team RWBY and they initially mistake him for a threat. But as they get to know him, they find out he has valuable knowledge about some ancient Grimm - related secrets that could help them in their fight. So they form an uneasy alliance at first which gradually turns into a strong friendship.
One great fanfiction is 'Blake's New Beginning' where the male reader character enters Blake's life at a crucial time. It shows their relationship developing gradually through various adventures. The story does a great job of staying true to the RWBY universe's essence.
Well, loyalty is a big one, as Tyrian is very devoted to Salem. Power dynamics are also common, like how Salem's power over Tyrian affects their interactions. The theme of manipulation can be present too. Salem is a very manipulative character, and in fanfiction, this can be explored in relation to Tyrian. There could be themes of trust and betrayal as well. For instance, would Tyrian ever betray Salem, or vice versa? And sometimes there are themes of the unknown or the mystery of their relationship. Writers might try to fill in the gaps of what we don't know about how they truly feel about each other.
There are definitely some out there. Some might explore the dark and twisted nature of their possible relationship within the context of the RWBY universe. However, the quality can vary a lot. It's important to read reviews or summaries before diving into a particular fanfiction to make sure it meets your expectations.
Power is a common theme. Often, the OC either gains power from Salem or has to deal with Salem's overwhelming power. Another theme is loyalty. The OC may struggle with being loyal to Salem or may have their own sense of loyalty that conflicts with Salem's goals.
One great fanfiction in this category could be 'The Encounter with the Female Grimm'. It has an interesting plot where the male reader character stumbles upon a unique female Grimm. The story is filled with action and adventure as they interact in a post - apocalyptic RWBY world.