One great 'Fate Stay Night Merlin Fanfiction' is 'Merlin's True Role'. It delves into Merlin's backstory and how his magic could have influenced the events of the Holy Grail War in ways not shown in the original. It has a really interesting take on his relationship with the other servants as well.
Merlin is obviously one of the main characters. He is a powerful wizard with great influence. Then there's probably Arthur, as it is related to Arthurian legend. There might also be other knights or magical beings that play important roles in the story.
One interesting Fate Merlin fanfiction could be about Merlin guiding a young and inexperienced mage in the modern Fate universe. This could involve him using his ancient magic knowledge to help the new mage face challenges.
Fate never let go of the poor. Although this saying was a common saying, it conveyed the point that unlucky people were more likely to encounter bad luck. This was because life was the same as people. They tended to bully the weak and fear the strong. They despised the poor and loved the rich. Poor people often lacked self-confidence and were easily bullied and oppressed. On the contrary, rich and powerful people were more likely to be treated well in life. However, this was only a point of view. It was impossible to determine whether fate really intended to choose the poor.
The story length of Fate/GO can vary depending on how much content you explore. But generally, it's quite extensive and can keep you engaged for a considerable amount of time.
The story length of Fate/GO can vary depending on how much content you engage with. But generally, it's quite extensive and offers hours of gameplay and narrative.
Fanfiction.net is also a possibility. There are many Fate Stay Night fanfictions there, and if you specifically search for Merlin - centric ones, you might find some gems. However, the quality can vary more compared to AO3, so you might need to do a bit more sifting through the results.