This beauty is an illustration from a northern Italian compendium of canon law, early 9th-century AD. It shows Constantine presiding over the Council of Nicaea—the lettering makes Ns look a little like Hs, but you can see the writing at the top there: SINODUS NICENI—and under the throne (helpfully labelled ‘CONSTANTINUS’) are a great many stooping monks stuffing Arius's books onto a fire: heretici arriani damnati. The Latin damno means I find fault, I reject, as well as referring to punishment, guilt and condemnation, so you'd probably translate this ‘Arius's heretical writings are rejected’ rather than ‘... are damned’.
I like the way this image's perspectivelessness makes it look as though the monks are lighting a fire underneath Constantine, like a swarm of diminutive Guy Fawkeses. Also: what kind of gesture is the emperor making with his right hand? Of course we're all aware of the pictoral convention in religious art by which the gesture of the hand communicates the holiness of the sitter, the fingers picking out the letters of Christ's name:
But Constantine isn't doing anything so precise with his hand. It looks, rather, as if he's just waving at us. Hiya!
[In case you were wondering, the positioning of the fingers on that hand is the same gesture priests would perform during the liturgy to invoke Christ's name, as explained by this chart]