However this is to be translated I really do not think this is a Black Mass, or anything to do with witchcraft. The object the women hold is far larger than any medieval host I have ever seen in a contemporary illustration - even those enclosed in a monstrance to be held up for adoration during a procession are far smaller. According to the Malleus Maleficarum¹ witches who stole Hosts did so by concealing them under the tongue or surreptitiously slipping them from mouth to handerkerchief, neither of which would be possible with something of this size. There are paintings and woodcuts of Black Masses in existence (those I have seen date from the 15th century)² but these invariably feature the osculum infame (‘unholy kiss’) and feature the Devil in the shape of a goat standing patiently (but sometimes with a knowing smile) while groups of women and men queue to kiss his rump. They do not remotely resemble this painting. Moreover, if these women are knowingly and willingly servants of Satan, then he shows himself an ungrateful master here. The devils here are in fact shown in precisely the same relationship to the women as those in the Warning Against Idle Gossip - in other words the women are doing the Devil’s work, but only unwittingly so, I think, in the sense that they are distracted from holy things by wordly, frivolous and ‘idle’ ones.
There remains the mysterious inscription on the scroll held by the chief devil. Tristram suggested that ‘CELIA’ was a misreading, and suggested ‘cellam’ - ‘the secret place, or storehouse’ of the Devil. Alternatively, he thought, the correct reading might be ‘gauda’ - ‘the Devil’s gaud, or jewel’.³ The idea of a place where the Devil conceals himself seems to me the more plausible of the two, and I wonder whether this object is actually a mirror. In itself, the mirror is often used to symbolise vanity, and there are proverbs about women looking in mirrors in certain conditions or at certain times of the day/month/year and seeing the Devil reflected there. A painted table-board showing the Seven Deadly Sins by Hieronymus Bosch⁴ (active 1474; died 1516) shows Pride (‘Superbia’) as a woman adjusting a fancy headress and looking in a mirror. She sees only her own face reflected, but we see that the mirror is held by a devil half concealed by a cupboard and wearing, in grotesque parody of the woman, a headdress similar to her own. So perhaps this is a very imaginative warning about female vanity, a subject much preached about and generally inveighed against. At all events I think it is far more likely to be that than a Black Mass. But ideas and opinions about this painting - I have never seen another like it - would be very welcome.

¹J.Sprenger & H.Kramer, Malleus Maleficarum (Hammer of Witchcraft)1486, p.85-86, Folio Society (abridged edn.) 1968
²EW Tristram, English Medieval Wall Paintings : The 14th century, London, 1954, pp.111
³One is in the Bibliothèque Nationale, Paris, another in the Bodleian Library, Oxford [MS.Rawl D410fl]
⁴This painted table-board is still in the Prado Museum, Madrid, so far as I know.