Kalaka is a powerful Gaṇa. (A gaṇa is a deity associated with Lords Shiva and Ganesha; they live at Kailasa.)
Shiva Purana 2.2.33 says:
O sage, Kuṇḍī the most excellent of the Gaṇas and Parvataka went each with twelve crores in order to destroy Dakṣa’s sacrifice:
Kāla, Kālaka and Mahākāla went to the sacrifice of Dakṣa with a hundred crores.
and 2.1.20 says:
15-16. Viṣṭambha and Candratāpana each with eight crores, the leader of Gaṇas Mahākeśa with a thousand crores.
Kuṇḍin, Vāha and the auspicious Parvataka with twelve crores each, Kāla, Kālaka and Mahākāla each with a hundred crores.
Agnika with a hundred crores, Abhimukha with a crore, Ādityamūrdhā and Dhanāvaha each with a crore.
Sannāha and Kumuda with a hundred crores, Amogha, Kokila and Sumantraka each with a crore.
Your Shiva Purana story seems to be the only place where Mahesha, Sarada, and Vaitala are mentioned, though a line in the same Purana treats 'Mahesa' as another name for Shiva. Otherwise, these avatars are never again mentioned.
Obeisance to Thee, O lord, from whom the mobile and the immobile beings have originated. Obeisance to the great Puruṣa, Maheśa, the supreme Īśa and the great Ātman. [2.2.15]