Fredrica is the first magical damage dealer you get in Triangle Strategy, and as the name suggests, she utilizes fire magic. She has poor offensive stats and health, so keep her away from enemies and use her long-range fire attacks.
Fire spells do area of effect damage, meaning they can hit five tiles on the map at once. Since enemies also try to get back/follow-up attacks, they often group up, allowing Fredrica to pick them off from afar. The only downside to this is that she has pretty slow speed, so enemies may move out of range before her turn comes around. Giving her an accessory to help with her speed may be a huge boon to her shortcomings.
Fredrica has a passive skill that is automatically applied that boosts her fire damage but lowers her defence against ice magic. There are lots of ice mages in the Hyzante route of chapter three, so be careful not to get her surrounded.
Using her flame spell does use two turn points, so it can’t be used constantly. If you’re nearing the end of the fight and only a few enemies are left, throw her in the mix if she has no TP and dish out some physical damage.