Final Ascension Art is referring to the Stage 4 Variant of a Servant's (the gacha characters in Fate/Grand Order) Card Art. The Stage 4 art showcases the character in a way that is both dynamic and suits the character.
Final results will vary based on prompt used, so feel free to experiment. Hi-res is good to use.
Recommended keywords to use in addition: floating, dutch angle
If, for whatever reason, you want an Aspect Ratio closest to Servant Card art: 768×1088, 896×1272
