Amulet of Echoes

You reach out into the multiverse and summon a shadowy echo of yourself, an alternate version of you from an alternate timeline that never happened. The echo appears within 30 feet of you, has its turn immediately after you, and follows your verbal commands. It cannot speak but does understand all languages you do. It has the same Armor Class, proficiencies, and ability scores as you do. It has a quarter of your hit points and the same basic weapons that you do (for example, if you have a magical +3 longsword, it simply has a longsword), all weapon attacks being considered magical for the purpose of overcoming resistance and immunity to non-magical attacks. It knows all spells you do. The echo remains for the duration or until it casts a spell.