Well, Rhea was originally a elf which then got transformed into fey'ri (demonic elf) so it's custom race similar to tiefling albeit some elven racials/features mixed in. Along with custom made tattoo of power (demonmark, not dragonmark) and then class wise I recall she was bard|warlock, so in 5th edition she would either be multiclass or just have warlock's eldricth blast through a feat.