Complex sentence: Armed with the power he got from Brahma, he went to Mount Kailasha, the abode of Shiva, in the guise of a snake, because snakes were allowed to enter Kailash freely.
Split into simpler sentences: Armed with the power he got from Lord Brahma, he went to Kailash, the abode of Lord Shiva, in the guise of a snake. Since snakes were allowed to enter Kailash freely, he managed to enter Kailash freely.