Plana

The main OS of the Shittim Chest and Arona from another timeline. She is the manifestation of the damaged Shittim Chest from alternate timeline shot by Shiroko Terror, before reactivating when Phrenapates appeared. In the alternate timeline, A.R.O.N.A used to be the AI to confront the Alternate Sensei aka Phrenapates from the incoming doomed world of Kivotos, unfortunately the Shittim's chest has been shot by Shiroko Terror but remained Online despite the damage it takes. In the current timeline: Before the Assault of the Atrahasis-Ark, A.R.O.N.A Controls the entire fortress instead of Kei, A.R.O.N.A is also guarded by Phrenapathes and Shiroko Terror long before the Assault. After the Destruction of the Naram-Sin and the entire Atrahasis-Ark, A.R.O.N.A's systems were affected in the destruction, corrupting her systems and fading away but not long before the current Arona rescued her from certain fate, forcing the Shittim Chest to integrate the systems to save Sensei from his/her uncertain death. Desginer: DoReMi (Source: Blue Archive Wiki)