20,000 Martyrs burned in Nicomedia

Reading from the Synaxarion:

All these Saints, some 20,000 in number, were burned alive in the
year 303, while they were gathered in church. This came to pass during
the reign of Diocletian and Maximian. According to the Synaxarion,
this took place on the day of Christ's Nativity. Eusebius (Eccl. Hist.
VIII, 6) says that, of the Christians then living in Nicomedia, all
were slain by imperial decree - some by the sword, and others by fire,
and that, because of their divine and inexpressible ardour, both men
and women cast themselves into the fire. Besides those burned in
church. the following, who were slain in the same Persecution, are
commemorated today. Indus, Gorgonius, and Peter were cast into the sea;
Glycerius the Presbyter and Mardonius were burned; Dorotheus the Prefect
and Zeno were beheaded; Theophilus the Deacon was stoned; Mygdonius
was buried alive; and Domna, who had been a priestess of the idols,
believed in Christ, and was baptized, was beheaded and cast into the fire.
See also the account of Saint Anthimus on September 3.

Apolytikion in the Second Tone
Blessed is the earth that drank your blood, O prizewinners of the Lord,
and holy are the tabernacles that received your spirit; for in the
stadium ye triumphed over the enemy, and ye proclaimed Christ with
boldness. Beseech Him, we pray, since He is good, to save our souls.

Kontakion in the First Tone
A twenty-thousand numbered battalion of Martyrs ariseth like an
unwaning star great with brightness, enlight'ning by faith the hearts and
the minds of all godly folk. For, enkindled with divine love unto
the Master, this courageous host received a sanctified ending when
eagerly burned with fire.