Adam or any other monster could absorb Arnoth and Lost Light's energy. Even though Adam was human and couldn't absorb energy from the environment, it was still possible to do so under some special circumstances.
The golden orb wouldn't help him immediately become a K4-Phantom, but the Evolution Tree might be able to devour it and become a bit stronger. Arnoth's energy became dense, resembling an essence, moreover, the sphere also contained the energy of Lost Light, which was an External Artifact.
But, it was to fulfill the last wish of not only Arnoth but also the Crimson Monarch.
Moira opened her eyes, light falling on her shocked face.
Baffled, she slowly turned around, facing Adam's exhausted but kind gaze.