Personality differences between Nero’s Phase 1 form and his Phase 2 form:
Phase 2 has inherited a good chunk of Or’s omnicidal tendencies and lack of empathy, referring to everyone he thinks is beneath him with terms such as food or prey, or the like.
Is less duty-focused. While he certainly aims to link the flame so hard that it’ll last so long that people might as well forget about the cycle, he certainly thinks that he could fulfill what his mother wants to (which is to end the world by her own hands in a sort of weird “better to die than be killed” kind of philosophy) before the flame goes kaput forever.
While Phase 1 prominently uses his bitchin’ sword, Phase 2 is more savage and utilizes his claws and only uses the sword for special attacks. (Phase 1′s sword is actually a physical object, Phase 2′s “sword” is more like this sharpened clump of magic)
Phase 2 is less composed than Phase 1 overall, more likely to toy with his enemies physically rather than be combat pragmatic like Phase 1 is.