They overcame him by the blood of the Lamb and by the word of their testimony; they did not love their lives so much as to shrink from death. - They overcome Satan by the blood of the Lamb, they are freed of their sins by the blood of Jesus (1:5), therefore the basis of his accusation has gone because the penalty has been paid by the blood of Jesus, so when he accuses them they point him to the blood. Hence Paul can write 'Who will bring any charge against those whom God has chosen? It is God who justifies' (Rom 8:33. They overcome Satan's lies in the world through the words of their testimony to Jesus. They overcome Satan because in the end they are prepared to die for their faith. When Christ died on the cross the saints were technically in Christ and therefore share in his victory, Rom 6:5-14. The results of this victory can be seen in James admonition to resist the devil and he will flee from you (James 4:7). It is seen by the spiritual warfare of Eph 6:11-18, in which the shield of faith is used to extinguish the flaming arrows of the evil one. Col 2:15 tells us that by the cross Christ has disarmed the powers and authorities and triumphed over them.
Just as Jesus overcame Satan by his death on the cross so Christ's followers must follow His example. The basis of his accusations has become null and void because they have been freed from their sins by the blood of the Lamb (Rev 1:5, 7:14, Col 1:22, Rom 8:33, 1 John 1:7), they testify that Jesus is the Christ (resulting in their salvation Rom 10:9-10) and prove the genuineness of their faith by being faithful unto death and thereby gained their life (Rev 2:10, 2:13, 6:9, 11:7, Luke 14:26, 21:16). Even death does not defeat them (Rev 6:9), just as Jesus achieved victory over Satan through death, the saints do likewise. Once more a reference to those who are martyred, a recurrent theme of the book. Later in 13:7 we find the beast waging war against the saints and defeating them but in 15:2 we also find those who are victorious over the beast in heaven singing the song of Moses and of the Lamb.
