Morney is an amazing support, helping with healing, dmg increase, tone responses (+more tune related buffs with lynea)
With her sig weapon she give 20% crit dmg when on her special field.
She has a 100% crit rate on her ult like Shorekeeper on her intro skill. (Not sure cauz I haven't crit when I have her 4 cost crit dmg)
You don't need her weapon to make her work, her sig is just a plus not a requirement.
If sig (def scaler) She gains energy, crit dmg for team, and you build her : 4 cost def, heal bonus, crit dmg, 3 cost energy×2 or 1 energy1 def , 1 def ×2.
You want her ult as often as possible her special set requires you to get more or less 270 energy so try to get as much energy as possible.
She works on the rejuvenating glow set as well as the new set.
Same build on the 2 sets.
Hope I help u build your Morney
Cheers