Is 4* Fae (-HP +SPD) worth upgrading to 5*?

Why Fae to five stars?

Dont, fae is not that good

Wait for a good green to come along in one of the banners. I imagine Soren will be green whenever he shows up since we have so few green mages right now, and there is probably another green dragon on the way (Myrrh? Her color scheme is green at least) who you can try to pull at 5 stars.

Idk why people underestimate fae so much but to be honest I think -hp +spd fae is the ideal fae. I got a +spd -res fae and she puts in work on nowi, hector and takumi. If you give her fury she turns into a beast also with lightning breath or dark breath. IMO she is really underated because people dont prep for her and she can catch a lot of people off guard given how tanky she is for a magical green.

Fae is a pretty good unit with decent stats compared to other dragons, such as Nowi, Tiki, and Tiki (Young). A lot of people say she's bad, due to the fact that the current meta is mostly red units, but I wouldn't blame that on the unit being bad. Her skillset is pretty neat, with Renewal 3 allowing her to heal herself 10 hp every second turn, which sort of removes the HP problem, and Threaten Atk 3 granting debuffs to all enemies 2 spaces away from her. Fae's Light Breath provides a boost in def/res for adjacent allies after she attacks which works well with Threaten Atk. However, she is not tanky (25 def only), especially compared to many other dragon units, so that might be something you should consider before ranking her up. Let's not forget her Draw Back skill too. It's pretty handy in Arena.