The present graffiti was among various pieces discovered on the walls of a cryptoporticus (underground corridors) near the Roman theatre (the Odeion) in Thessaloniki, which was built in the first century CE:

https://en.wikipedia.org/wiki/Roman_Forum_(Thessaloniki)#/media/File:Thessaloniki_odeion_August_2_2006.jpg.

The graffiti cited above invokes the help of the Lord God for two individuals, Eutychos and Elpidios, and is found close to other graffiti (which can be seen in the attached image) which has led to its interpretation by Pallas and others as testimony of the Christians who died in the arena during the persecution under Diocletian. In Pallas’s words (I translate from the French), the accompanying graffiti shows “an attacking panther, a ship, a symbol of the passage to the port of eternity … a pediment resting on two pillars, on which hangs a crown, a symbol of triumph and the entrance to the heavenly palace in paradise” (“Investigations sur les monuments,” p. 2). The so-called Great Persecution of Diocletian was the last persecution of Christians at the hands of Rome, and began in 303 CE after Diocletian had consulted the oracle of Apollo. Some scholars have suggested that Christian authors have greatly exaggerated the scale of Diocletian’s persecution (see, for instance, the influential article of Geoffrey de Ste. Croix, “Why Were the Early Christians Persecuted?”). It seems that Diocletian’s edict against the Christians of 304 CE was enforced in Thessaloniki in the April of that year (see Timothy Barnes, Constantine and Eusebius, p. 24).

While it cannot be proved with absolute certainty that the graffiti represents some of the Christians condemned to die in the arena under Diocletian, the combination of the symbols depicted certainly lends itself to such a reading. This source therefore potentially offers us not only a fascinating piece of non-literary evidence of the persecution itself, but also some insight into how Christians responded to the situation from somewhere other than the martyr acts, which were highly stylised and embellished by early-Christian authors in order to maximise their polemical value (for example, see the commentaries on the Martyrdom of Polycarp, the martyrs of Vienne and Lyon, and the Acts of the Scillitan Martyrs). If this graffiti does in fact invoke God’s help (perhaps for as swift a passage as possible to heaven) for two unlucky Christians, then it provides a very real depiction of their hope of eternal salvation after their suffering at the hands of Rome (the symbols of the ship, crown, and palace can all be seen as indicative of this, as Pallas argues). In effect, the power of God is invoked for Eutychos and Elpidios as a direct counter measure to a violent expression of Roman imperial power.