A.T. Robertson Commentary Revelation 18:24

"And in her was found the blood of prophets and of saints, and of all that have been slain upon the earth." — Revelation 18:24 (ASV)

In her (εν αυτη). In Rome.

Was found (ευρεθη). First aorist passive indicative of ευρισκω. See 16:6; 17:6 for the blood already shed by Rome. Rome "butchered to make a Roman holiday" (Dill, Roman Society, p. 242) not merely gladiators, but prophets and saints from Nero's massacre A.D. 64 to Domitian and beyond.

Of all that have been slain (παντων των εσφαγμενων). Perfect passive articular participle genitive plural of σφαζω, the verb used of the Lamb slain (5:9,12; 13:8). Cf. Matthew 23:35 about Jerusalem.