With this angel
Of the heavenly host.
καὶ ἐξαίφνης ἐγένετο σὺν τῷ ἀγγέλῳ πλῆθος στρατιᾶς οὐρανίου αἰνούντων τὸν Θεὸν
Luke said that suddenly (καὶ ἐξαίφνης), a whole choir or a heavenly host of angels came to join this one angel (ἐγένετο σὺν τῷ ἀγγέλῳ πλῆθος στρατιᾶς οὐρανίου). They were all praising God (αἰνούντων τὸν Θεὸν). This one angel became a multitude of angels.