Two paths out
Both routes start at the Crossroads and run four biomes to a final boss.
Underworld route
Erebus (Hecate) → Oceanus (Scylla) → Fields of Mourning (Cerberus) → Tartarus (Chronos). Ends at Chronos; drops Zodiac Sand, used to stop him reforming.
Surface route
City of Ephyra (Polyphemus) → Rift of Thessaly (Eris) → Mount Olympus (Prometheus) → The Summit (Typhon). Ends at Typhon; drops Void Lens. Collect 4 Void Lens + Zodiac Sand + the Gigaros weapon to truly kill Typhon.
The Surface is locked at first
You must cast Permeation of Witching-Wards (3 Moly, 1 Cinder, 1 Shadow) to open the Surface entrance. Even then Melinoë drains health there until you cast Unraveling a Fateful Bond (2 Lotus, 2 Moss, 2 Nightshade, 2 Thalamus).
Different loot, parallel progress
The two routes do not share resources — each biome pays its own set (see the resources guide). Run both; they feed different incantations.
Pick by what you need
If your next incantation needs Surface materials, take the Surface. If it needs depths, take the Underworld. The wrong route delays the unlock by a full extra loop.