The main Yagna (fire-ritual) described in the Vedas is the Soma Yagna, where a drink taken from a plant (whose identity was lost) is offered. But the Vedas also describe some less important Yagnas, and in the Taittiriya Samhita of the Yajur Veda, the Fourth Prathaka of the Third Khanda describes some Yagnas that are optional. Here is one of the verses chanted during such a Yagna:
iii. 4. 5. a Agni overlord of creatures, may he help me; Indra of powers, Yama of earth, Vayu of the atmosphere, Surya of the sky, Candramas of Naksatras, Brhaspati of holy power, Mitra of truths, Varuna of waters, the ocean of streams, food of lordships overlord, may it help me; Soma of plants, Savitr of instigations, Rudra of cattle, Tvastr of forms, Visnu of mountains, the Maruts of troops overlords, may they help me.
Some of these are understandable, like Surya the Sun god being overlord of the sky, Chandra the Moon god being overlord of stars (as described in the Bhagavad Gita), and Shiva being overlord of cattle (which is why he's called Pashupati). But my question is, why is Vishnu described as overlord of mountains? What connection does Vishnu have to mountains in particular?
Could this be related to the Rig Veda describing Vishnu as a mountain-roaming bull, which I discuss in this question? Or could this be related to Venkateshwara (the Vishnu deity in Tirupati, AKA Balaji or Srinivasa), who is called the lord of seven hills?