Eru Ilúvatar
During the Second Age, Valinor performed a single action: the building of the island of Númenor as a reward to the Edain (who had fought with the Noldor). Soon, the kingdom of Númenor grew powerful, and even invaded Valinor. Then Eru Ilúvatar was called upon by the Valar and the island was destroyed, Aman was lifted out of Arda, and the world was bereft of Valar. Arda then became spherical and was left for Men to govern.