Gunslinger

She could see Altair, which was a bit of a surprise.

At first, Arad thought that Grace's psychosis made her see people weaker than her as shadows. But since she couldn't see Kali, that idea was immediately debunked. It wouldn't even make sense in the first place, as he was stronger than her.

Arad wanted to test many things, but Grace ended up carrying herself and went inside the vault and met Luminous. From what Arad understood, she could see it without suffering any damage from the blinding radiance.

This could be just due to elemental compatibility, like shadows dampening the light, but would that make sense for her to see Arad and Altair? Probably, since the void is the lack of anything and everything, including light, the same way as shadows.