Demonic Tutor from exile by paying ({1} magic symbol) ({B} magic symbol) , unpreparing
Emeritus of Woe.
When you cast that spell,
Spellweaver Helix's last ability triggers, allowing you to cast a copy of the Extra Turn Sorcery without paying its mana cost, causing you to take an extra turn after this one.
Resolve the copy of
Demonic Tutor, finding
Siege-Gang Lieutenant and putting it into your hand.