The Halo UNSC and Star Trek's Federation could form an alliance. The UNSC's focus on survival in a war - torn galaxy could be complemented by the Federation's ideals of exploration and cooperation. Characters from both sides would have to overcome cultural differences. For example, the more militaristic nature of the UNSC compared to the diplomatic - first approach of the Federation. This would lead to a lot of character development and interesting story arcs as they work together towards common goals.
In a crossover, the Elites from Halo might interact with the Vulcans from Star Trek. The Elites' honor - based culture could be compared to the Vulcans' logic - based society. They could start off as adversaries, perhaps misunderstanding each other's motives, but then gradually come to respect one another as they learn more about their respective cultures and values.
The characters could start off as enemies. For example, the Covenant leaders might view the Star Trek captains as heretics. But as the story progresses, they could find common ground in the face of a greater threat like the Borg or the Flood.
The logical Spock from Star Trek might be fascinated by the Transformers' mechanical nature and try to analyze them. Captain Kirk, on the other hand, would likely be more bold and adventurous in his interactions, perhaps even challenging the Autobots or Decepticons. Optimus Prime would probably see the Star Trek crew as potential allies in the fight for peace and justice, and he would approach them with respect. Megatron, of course, would see them as either threats or potential tools for his own evil plans.
The military - minded characters from Stargate, like Jack O'Neill, would likely be initially cautious and somewhat skeptical of the more diplomatic Starfleet officers. However, they would soon realize the value of Starfleet's knowledge and resources. On the other side, Starfleet officers might be intrigued by the Stargate technology which seems so different from their own. For example, Captain Kirk might be eager to explore through the Stargate.
The Spartans from the Spirit of Fire would likely be very formal and military - like in their interactions. They might be a bit cautious around the more laid - back Star Fox crew at first. For example, they would greet each other in a very military protocol - based way. The Star Fox team, on the other hand, would be more friendly and open, trying to break the ice with the Spartans.
One idea could be the Covenant from Halo encountering the Borg from Star Trek. The Covenant's religious zealotry and advanced technology would clash in an interesting way with the Borg's hive - mind and assimilation capabilities.
The characters could interact through a portal that links their two worlds. For example, Master Chief could end up in Berk and be initially seen as a strange and powerful warrior by the Vikings. Hiccup, being the curious and open - minded character he is, would be the first to approach the Chief and try to communicate. They could then start to exchange ideas about their respective worlds and threats they face.
If we consider the abilities of Servants in Fate and Spartans in Halo, it's really interesting. Servants have magical powers like Gilgamesh's Gate of Babylon which can summon countless weapons. Spartans, on the other hand, have their advanced combat training and high - tech armor. In a crossover, a Servant's magic might be able to disrupt a Spartan's high - tech equipment. For example, a lightning - based magic attack could short - circuit some of the Spartan's systems.
They could interact through combat. For example, the Spartans might fight alongside the SG teams against a common foe like the Covenant or a powerful Goa'uld army. The Spartans' combat skills and advanced armor would be a great asset in the Stargate universe battles.
The characters might initially be cautious of each other. For example, Shepard from Mass Effect could be skeptical of the Star Trek crew's non - violent approach at first. But as they get to know each other, they could start to share their skills. The Star Trek crew could teach Shepard about their advanced medical techniques, while Shepard could show them some combat maneuvers.
Star Trek, without a doubt. Consider Picard. He has to balance his role as a Starfleet captain, a diplomat, and a moral leader. His backstory, his relationships with his crew, and his beliefs all contribute to a very complex character in fanfiction. In Halo, the main characters are usually soldiers. While they can be interesting, they don't have the same level of depth as Star Trek characters. They are mostly defined by their combat skills and loyalty to the UNSC. However, Halo does have some characters that are starting to get more complex in recent fanfiction, but still not on the same level as Star Trek.