I've also heard about 'Lust and the Elric Brothers' Crossover'. This fanfiction delves into how Lust's presence could change the dynamics between Edward and Alphonse Elric. It has some exciting action scenes as well as some emotional moments that are really well - written.
Often, these fanfictions blend the dark and complex world of Fullmetal Alchemist with the idea of 'lust' which could be in terms of a character's desires or a new, alluring force in the story. They might also explore different character relationships and how 'lust' can either strengthen or disrupt them.
There's also 'Homunculus in Another Realm'. In this fanfic, the homunculi are sent to a parallel universe. It has an interesting plot where they interact with new characters and face different challenges than in the original FMA world. The author does a great job of portraying their personalities in this new setting.
I'm not sure about a specific one off the top of my head. But you can try searching on fanfiction.net or Archive of Our Own. They usually have a wide range of crossover fanfictions.
One great fma scar crossover fanfiction could be where Scar teams up with a character from another universe to fight a common enemy. For example, a crossover with a character from Naruto. Scar's unique alchemy skills combined with the ninja's jutsu would make for an exciting plot.
A lesser - known but very creative fma envy crossover fanfiction is the one that combines the world of FMA with a steampunk - themed universe. Envy has to adapt to the new rules and technology in this world, and the story does an excellent job of showing this transformation.
Another interesting one is 'Alchemic Ninjutsu'. In this fanfiction, the concepts of alchemy from FMA are merged with the ninja techniques in Naruto. The author does a great job of creating new jutsus based on alchemical principles, and the story follows a group of characters as they explore this new form of power.
First, know both universes well. For an fma crossover, you need to understand the rules of alchemy in FMA and the characteristics of the other universe you're crossing it with. For example, if it's a Star Wars crossover, know about the Force and lightsabers as well as alchemy.
Some fma crossovers involve characters from DC Comics. Picture Batman or Superman in the world of FMA, dealing with the concept of equivalent exchange and the political intrigue in that world. It can lead to some really unique storylines and character interactions.
First, know the characters well. Understand Greed's personality, his desires, and his powers in FMA. Then, research the other fandom you want to crossover with. Next, create a unique and engaging plot that combines elements from both worlds in a seamless way. For example, if it's a crossover with a fantasy world, think about how Greed's alchemical nature would interact with magic. Don't forget to develop good character relationships and let the story flow naturally.
There's 'The Vampire's Allure' which is known for its vivid descriptions of vampire allure and the lustful undertones in their interactions. It's a great read if you like detailed character development along with the vampire lust theme. Well, the story builds up slowly, introducing the characters and their world, and as it progresses, the lust aspect becomes more prominent, adding to the overall allure of the story.