Wizard Frumscone can be found in the basement of the Wizards' Guild, where he summons magical zombies. He is involved in the Swan Song quest, but does not play much of a role, as he sends you to speak to Malignus Mortifer instead. He wears robes similar to wizard robes.
Sometimes, you may find a clue scroll with the anagram OR ZINC FUMES WARD, which unscrambles to Wizard Frumscone, and when you talk to him, he will give you a puzzle box. After solving it, talk to him again to receive another clue scroll or the treasure trail reward.