One of the popular misconceptions of the dogma of transubstantiation is that the accidents of the bread and wine after consecration are mirages, illusions, or figments of the human imagination. No. You really saw the visible accidents of bread and wine before the substantial change, and you really see the visible accidents of bread and wine after the substantial change. There is no element of mirage, illusion, or deception. The difference is that, before consecration, the accidents of bread and wine inhered in their proper substances (bread and wine) and signified to your senses the presence of that substance. After consecration, those accidents are miraculously sustained despite the underlying substantial change. Now, the accidents (which are just as “real” in the common English-language meaning of that term as the changed substance is) signify the Body and Blood of Christ present sacramentally. Without the retention of the accidents as signs, transubstantiation alone would not constitute a sacrament. The bread and wine persist only as accidental signs of a higher supervening* substance, not as substances in their own right/rite.
Contrast this with the other sacraments, where the water, oil, etc., become signs accidentally, but still remain substantially water, oil, etc. They retain their own natural identities. The water, etc., are accidentally instruments of grace while substantially remaining unchanged. In a far more august change, the bread and wine substantially become instruments of grace (i.e. the very Instrument of Grace, the Humanity of the Word Incarnate) while remaining bread and wine only accidentally, i.e. sacramentally. Considered from the perspective of both accident and substance, the bread and wine are totally consumed (i.e. they wholly terminate) in the sacrament. Regarding their substance, the bread and wine are transformed into the Body and Blood of Christ the Head. Regarding their accidents, the bread and wine are transformed into the body and blood of Christ’s Mystical Body, the Church. It is a hylomorphic holocaust.
*”Supervening”: by conversion of the bread and wine into the Body and Blood of Christ, not by mere substitution. What was bread is now Flesh, what was wine is now Blood.