Source: TW
asura
“Asura” was not a “general term for deity” in the archaic Vedic (i.e. RigVedic) textual layers. It is instead a term for ‘mighty’, and is applied not only to some Gods but also Demons and even Humans therein. It doesn’t mean ‘Divinity’ or refer to a ‘Tribe of Gods’ [à la ‘Aesir’].
A good example would be the situation of Agni - labelled ‘Asura’ at RV VII 6 1, and an ‘Asura-Slayer’ at RV VII 13 1 (both from the very archaic ‘Family Books’).
Similarly, Indra’s ‘Asura-ness’ (“Asuratvaa”) at RV X 99 2 doesn’t conflict with His efforts at RV VIII 96 9 & RV VIII 97 1 to, basically, disarm (“anaayudhaaso”) ‘Asuras’ and relieve them of their ‘cool stuff’ (“bhuja”)
RV X 157 4 has “the Gods, [having] slain the Asuras” [“hatvaaya devaa asuraan”] ; whilst RV VIII 27 20 seems to have “Asuraa” to refer to the ‘All-Gods’ (‘Vishvedeva’) as a group; & RV III 55 13 speaks of “Mahad Devaanaam Asuratvam Ekam” - the Great & Sole Might of the Gods
Meanwhile, Svarbhanu - who is Very Definitely A Demon (and an A’Sura in later attestation; as an Eclipse Demon, doubly so), is “Asurah” (‘Asuric’) per RV V 50 5 & 9 - again, from the Family Books, the more archaic swathe of the RV.
a-sura
The fact of the demons being ‘anti-Solar’ is precisely why A’Sura as a hailing (a homophonic formulation for Asura, but of entirely different meaning & derivation) shows up for them.
suraH
The Gods, of course, being Solar - and with “Sura” utilized for Them ; (c.f. “Sūracakṣasaḥ” being, per Jamison/Brereton [I assume referencing Geldner] “characteristic of Gods; in I 89 7 it is used almost as a definition of such.” - at RV VI 1 110 4 the Rhbus attain this)
We can demonstrate this via looking at various of the Vedic occurrences wherein A’Sura has begun to show up , in the Brahmana layer of texts. For instance - SBr IV 3 4 21, where the A’Suras inflict Darkness (‘Tamas’) to disrupt the Rite, countered via Gold.
At SBr XI 5 5 1-6, we see the A’Suras acting not only against the Gods, but the Solar Realm [“svargaṃ lokaṃ”] through their projection of darkness. x.com
In any case, one finds various “Asurarakṣasa” utilizations in the SBr , in some cases these occur alongside “Rakṣas” [for instance, SBr IV 1 1 19 has the former, then next verse the latter], in others alongside “A’Sura” [e.g. SBr III 5 1 21 has both, .. and Rakṣas at 31 later]
It is certainly plausible that the ‘Asura-’ component to various of these “Asurarakṣasa” utilizations could mean “Asura”, ‘Mighty’ [at SBr III 5 1 21, an individual named Saharakṣas - the ‘Overpowering-Rakshasa’ - is dueling with Agni in a contest of Priestly invocation]
(And, for that matter, the fiends assailing the Gods at TS VI 2 7 4 & VI 4 6 1, who are equipped with Vajras - seriously, “Asurā vajram udyatya devān abhy āyanta” & “te ‘surā vajram udyatya devān abhy āyanta”, respectively, might be reckoned ‘Mighty’ for obvious reasons). There is a point I had intended to make about Agni specifically here, but my acuity wanders from me Perhaps another time.