What happens at the end of The Silmarillion?

At the end of The Silmarillion, the great struggles of the First Age culminate in the downfall of Morgoth, the dark lord, who is ultimately defeated and cast into the Void by the Valar. The remaining Silmarils, the powerful jewels created by Fëanor, are lost; one is taken by a star, another is consumed by fire, and the third is buried deep in the earth. The world undergoes significant change, leading to the rise of Men and the diminishing of the Elves, marking the transition into a new age. This conclusion sets the stage for the events of The Lord of the Rings.