Complex sentence: Befriending the Wiccan Leo Martello, he was introduced to Herman Slater, with whom he entered into a relationship and together they opened up an occult supply store, The Warlock Shop.
Split into simpler sentences: Befriending the Wiccan Leo Martello, he was introduced to Herman Slater, with whom he began a relationship. Together they opened an occult supply store, The Warlock Shop.