Thought:  Author's Notes

The title is from Tambourlaine The Great by Christopher Marlowe:

"Nature that fram’d us of four elements,
Warring within our breasts for regiment,
Doth teach us all to have aspiring minds."

"Greylin, Langwell, Sîr Ninglor, Celebrant, Limlaith, Onodló, Erui, Celos, Poros, Sirith, and even foul Morgulduin" - these are the major rivers and tributaries that flow to the Anduin.