Optimal Gronnblade Cecilia Build

Cecilia sits with 25 spd so most of the time +atk ivs are more helpful and thats why things like fury and death blow are recommended. Close Counter is for if you want to turn here into an anti dragon blade tome. Life and Death should only be used with +spd Ivs as she has 29 spd with + spd and life and death makes that 34, and add hone cavalry she has 40, but she is made super frail with L&D

Gronnblade+, Atk+ IV, and Hone/Fortify Cavalry if you don't have that on her yet. DB3 is great. G tomebreaker or Axebreaker are both ok, I'd lean G tomebreaker as she has good res to survive a partially bladed Nino. Alternatively, you could go for the Raven TA build. That lets her destroy both Blyn and Rein in the same turn. If you're facing higher merges, you might need some Distance Def 3 or Deflect Magic 3 seals to help with that. That build lets her one-shot Blyn through Mulagir's bonus cancelling. Merged +1 Raven TA with Atk+ IV is no joke. It's just a bit less good against the general field, but better against Blyn and Rein/Olwen, so it's probably worth it imo.

I run Fury on my Blade Cecillia with ATK IV. She still sits at 38 res with Fortify which is pretty respectable and good to have against most Blue tomes. G Tomebreaker secures wins against another Cecillia, BTome Ninos and Julia, all of whom Cecillia would never naturally double. Regardless of build shes still frail against physical damage so just avoid those Brave Lyns as much as possible when not running Raven.

Because her base spd is not meant to blade tomes, it is really bad, sure u can catch up with buffs and seal but she is gonna be outclasses by any other green horse mage. She is really not fast and even with buffs and stuff she wont be doubling that much. So she better off focusing on one shotting units as her attk is pretty good and she can bait blue mages with easy.