There's plenty of ready-made Amaimon wigs out there (some of which look pretty cool!) - but the cosplayer asked for a real gradient, instead of the usual three-tone, layered styles.
I still used differently colored fibers as a starting point, but I dyed them varying shades of dark green and olive green with darker roots.
Dyeing dark colors isn't much fun, and it's particularly hard to achieve dark tones on light, vibrant fiber colors. Still, I hope you like the result.
1 mid-length wig (light green), extensions x2 (light green and lime), wig dye (dark green/grey/brown mix); foam core (craft foam)