Brahma created Rudra to help him in his creative endeavor, but from the very beginning Rudra began to devour the whole creation, and thus he had to be stopped from such devastating activities
SB Canto 3
Marīci, Atri, Aṅgirā, Pulastya, Pulaha, Kratu, Bhṛgu, Vasiṣṭha, Dakṣa, and the tenth son, Nārada, were thus born.
The whole process of the creation, maintenance and dissolution of the cosmic manifestation is meant to give the conditioned souls a chance to go back home, back to Godhead. Brahmā created Rudra to help him in his creative endeavor, but from the very beginning Rudra began to devour the whole creation, and thus he had to be stopped from such devastating activities. Brahmā therefore created another set of good children, who were mostly in favor of worldly fruitive activities. He knew very well, however, that without devotional service to the Lord there is hardly any benefit for the conditioned souls, and therefore he at last created his worthy son Nārada, who is the supreme spiritual master of all transcendentalists. Without devotional service to the Lord one cannot make progress in any department of activity, although the path of devotional service is always independent of anything material. Only the transcendental loving service of the Lord can deliver the real goal of life, and thus the service rendered by Śrīman Nārada Muni is the highest among all the sons of Brahmā.