Which character gains the ability to breathe Pandora's air in Avatar: Fire and Ash? The answer is Spider.
Spider, whose human name is Miles “Spider” Socorro, is a human teenager raised among the Na’vi and the Sully family. Unlike the Na’vi and human-controlled avatars, he normally needs an exopack or breathing mask because Pandora’s atmosphere is unsafe for unmodified humans.
In Fire and Ash, Spider’s mask loses power while he is separated from the others. Kiri reaches through her extraordinary connection to Eywa and infuses his body with Pandoran mycelia. The biological change allows Spider to breathe Pandora’s atmosphere without an exopack.
This does not make Spider a conventional avatar. He remains biologically human, but his altered body can also develop a neural connection, giving him a closer physical relationship with Pandora. Aonung, Neteyam and Lo’ak are Na’vi characters; they already breathe Pandora’s air naturally and do not undergo this transformation.