phantasma

The sudden presence of a raven at a bridal banquet could scarcely have been a greater phantasma.

Phantasma enim est sentiendi actus; neque differt a sensione, aliter quam fieri differt a factum esse.

The idea or phantasma, as he terms it, is the very perception or actus sentiendi.

Shakespeare seems to use it ('phantasma') in this passage in the sense of nightmare, which it bears in Italian.

Her ancient civility is gone, and her glory hath vanished as a phantasma.