Hmmm... how's Etheropod? I'm fusing Ethereal - in the mystical sense due to his angelic and psychic nature - and Arthropod. I realise it's not a true arthropod (no jointed legs), but it's not exactly a true seraphim either.
Also, throwing down my support for Glorifly and Apocalyx :) I'm not a fan of all the suggested ones that just use "seraph" and just add a syllable to the end, they are't imaginative and they don;t flow all that well.
I burned the dead wood to make the fire rise.
Blood of innocents, Burning in the Skies...