Seraphim
The seraphim appear in scripture only in Isaiah's throne vision, where they stand above the enthroned Lord, cry the threefold "Holy" antiphonally, and carry out the act that purges the prophet's lips. Their two appearances in Isaiah 6 are the entire textual record, and both belong to the same scene.
Six-Winged Attendants Above the Throne
In the year King Uzziah died, the prophet sees Yahweh seated on a high and lofty throne with his train filling the temple. The seraphim stand above him, each with three pairs of wings put to distinct use: "Above him stood the seraphim: each one had six wings; with two he covered his face, and with two he covered his feet, and with two he flew" (Isa 6:2). Two pairs serve a posture of self-veiling before the holy presence — face and feet shielded — and only the third pair is for motion. Their cry to one another, "Holy, holy, holy, is Yahweh of hosts," shakes the foundations of the thresholds and fills the house with smoke.
Agents of Cleansing
When Isaiah confesses unclean lips and undoing in the presence of the King, one of the seraphim moves from the antiphonal chorus to direct ministry: "Then one of the seraphim flew to me, having a live charcoal in his hand, which he had taken with the tongs from off the altar" (Isa 6:6). The same six-winged beings who cover their faces before Yahweh are the ones who carry fire from the altar to the prophet, so that touching the charcoal to his mouth removes iniquity and forgives sin. The seraphim are thus presented in two roles within a single vision — perpetual proclaimers of holiness and active mediators of cleansing for the one whom Yahweh is about to send.