Imagery of entanglement (yoke, bit, net, etc.) in Agamemnon have a specific purpose. What is that purpose?
The purpose of such imagery is to point towards the inexorable workings of fate that the characters are unable to avoid. It is interesting to reflect that all of the characters are shown in this play to be caught up in the net of fate and the tragic ending that awaits them all. Even those who appear to be victorious, such as Clytemnestra, is shown at the end of the play to have a delayed judgement that awaits her when her daughter, Orestes, finds out about what her mother has done to her father. Note the following reference to such images in this quotation from Cassandra, who protests about the fate that awaits both her, Agamemnon, and the rest of the characters:
Ah! Ah! What apparition is this? Is it a net of death? No, it is a snare that shares his bed, that shares the guilt of murder. Let the fatal pack, insatiable against the race, raise a shout of jubilance over a victim accursed.
Images of "net of death" and "snare" are particularly important. Both are presented as being related to fate and are described in terms that entangle. Even characters such as Cassandra who see clearly what is going to happen, both to her and to Agamemnon, can do nothing to free themselves from this snare and net that fate has prepared for them. Such images therefore serve to highlight the tragedy and the dramatic irony of the play: the audience, after all, knows how it will turn out, but only Cassandra among the characters is fully aware of how the tragedy will transpire.