Re: (Nutaku) Milenium War Aigis (English Version)
Is she worth using? Or did I pull one of those comparatively bad rares, like Hunter Stray?
She's not great, but a bit better than everyone's "beloved" golden bandit. And if you ever get him (trust me, you will. everyone gets Conrad or two - such is life), you can 30CC him and feed to her for Skill Up. Risk Life is one of the skill that really shine on higher levels - it's burst damage with no defense, so the more you squeeze out of it, the better.
That said, bandits are not the preferred duelist class most of the time. They suck outside of their skill. Don't look at high attack value - their attack rate is so slow rogues and valks outdamage them against all but most armored enemies. Not to mention they can't protect lanes: by the time bandit swings his ax twice, everyone and their mother will pass him.
So when you use her, plan a bit ahead, so by the time actual target connects you can activate skill and melt it.
Cellia is a bit different from the rest. She's a defensive bandit with a skill that cuts received damage from ALL your allies, has MR and very high (might as well be highest in the game) HP value. Aside from obvious sortie bonus for getting fairies, I use her as a first lighting rod when farming Immortal Beast. With skill active + her MR + her HP she survives for quite some time while mages destroy goatmen.
Edit:
Keep levelling up. You get quite a lot of unit slots on your way up in levels. And you will have to invest crystals in box expansion anyway, so if you feel immediate need, might as well do it now.