The Greek forms are:
They are formally treated as distinct nouns, and their exact etymological relationship remains disputed. But their phonetic and ritual convergence is undeniable. An ancient hearer could hear θρόνα / θρόνος / θρόνωσις together, especially when enthronement occurred during an induced initiatory state.
An ancient dialectal gloss preserved in the scholia says:
Αἰτωλοὶ δὲ τὰ φάρμακα [θρόνα καλοῦσιν].
The Aetolians call pharmaka throna.
Another ancient explanation is even more direct:
Θρόνα τὰ θραύοντα τὸν νοῦν ἢ τὰ θροῦν ποιοῦντα ἐν τῷ νοΐ.
Throna: things that break/disrupt the mind, or things that produce a disturbance within the mind.
Eustathius explains:
Θρόνα δὲ κυρίως μὲν τὰ ἐκ θηρίων ἢ τὰ ἐκ γῆς ἀναθορόντα ὀνήσιμα φάρμακα.
Properly, throna are the beneficial pharmaka arising from thēria or from the Earth.
That is stronger than simply “herbs.” Throna may be substances obtained from plants/Earth or from animals-ἐκ θηρίων. That leaves room for venom and other animal-derived pharmaka. The surviving ancient glosses are collected with their sources here.
In Theocritus’ Pharmakeutria, the woman first prepares an animal-derived drink:
σαύραν τοι τρίψασα κακὸν ποτὸν αὔριον οἰσῶ.
Having ground up a lizard, tomorrow I shall bring you a potent/harmful drink.
She immediately orders Thestylis to take the throna and smear them upon the entrance:
Θεστυλί, νῦν δὲ λαβοῖσα τὺ τὰ θρόνα ταῦθ᾽ ὑπόμαξον
τᾶς τήνω φλιᾶς καθ᾽ ὑπέρτερον…
Thestylis, now take these throna and secretly knead/rub them onto the upper part of his doorway…
The cluster is exact:
Theocritus, Pharmakeutria 2.58–62, Greek text
So the sequence makes sense:
In that ritual register, “sitting on the throne” can indeed operate like drug slang: being seated within, mounted upon, or stabilized inside the pharmakon-induced condition.
The throne is the outward office.
The throna are the inward ordeal that qualifies the ruler.
John says:
The drakōn gave the thērion its power and its throne.
A woman seated upon a scarlet thērion.
And:
The thērion carrying her.
She is simultaneously under the influence and in command of the scene:
I sit as Queen.
She is intoxicated by blood, causes the nations to drink her prepared wine, and leads them through pharmakea (φαρμακεία). The serpent gives the beast (thērion) its power and throne; the Queen sits upon and rides that serpent-derived power.
Thus “riding the beast” describes mastery of the throna-including the animal-derived pharmakon ἐκ θηρίων. The physical θρόνος marks the person who has survived, mastered and been transformed by the θρόνα.
She is Queen precisely because she can ride the venom without being destroyed by it.