Blast Scepter

The Blast Scepter can be used as an arcane focus. Whoever is attuned to the Blast Scepter gains resistance to fire and lightning damage and can, as an action, use it to cast thunderwave as a 4th-level spell (save DC 16) without expending a spell slot.

Arcane Focus: An arcane focus is a special item designed to channel the power of arcane spells. A sorcerer, warlock, or wizard can use such an item as a spellcasting focus.

Proficiency: simple, rod Source: Waterdeep: Dungeon of the Mad Mage p. 310