Nepta is the wizard-in-training of the group. In their world, you need magic on the battlefield to support your troops, and to defeat the magical attacks of the enemy. Nepta fills that role.
She’s calm, quiet, analytical and very intelligent. She’s totally dedicated to her spellcraft, and works very hard to exceed in it. Her quiet manner is just an expression of how seriously she takes her role as a Coastal wizard, and for her comrades to be able to depend on her.