Extremely powerful Servants whose general performance can compete even with higher rarity Servants.
Excellent Servants with strong all-around performance, or especially valuable niches. They are typically among the best in their class among the 4* Servants.
Great Servants that typically have more narrow specializations or face heavy competition. They often possess some unique factors that make them stand out.
Decent Servants that can perform well in the right teams, but often have either more powerful alternatives, or a niche that is difficult to fully exploit.
Servants with limited viability. These Servants can be viable, but typically require extensive support. Often they suffer from low stats, poor skills or ineffective Noble Phantasms. Still, dedicated Masters can extract good performances from them.