Quick answer
The Axatana is inside the Forgotten Tower in Mammon. Once the southern travel/corruption route is open, use the Outskirts/Castigator’s Keep side of Mammon, chain the Bone Gate traversal east to the Forgotten Tower, find the wall switch that raises the metal gate, defeat or bypass the lone guardian and take the weapon from the chamber.
What you need first
The real gate is not a character level. You need enough world progression to clear the corruption blocking the southern travel route from Marrow Keep and reach Mammon.
Once that route is open, most ordinary encounters on the way can be run past if you are only doing an Axatana rush.
Route from Mammon
Use these stable landmarks:
Outskirts of Mammon → Castigator’s Keep → eastern Bone Gate chain → Forgotten Tower → upper/remote tower chamber.
The exact micro-route includes several traversal launches and ledges. If you get turned around, prioritize the next Bone Gate rather than fighting every group on the battlements.
Open the locked chamber
At the final tower section, look for the wall switch/button beside the sealed metal gate. Activate it, enter the room and deal with the guardian inside.
The Axatana is the weapon pickup in that chamber.
Why the Axatana is popular
The weapon combines a fast katana-like light attack identity with heavier axe-style behavior. That flexibility lets it generate Resolve quickly and still exploit stagger windows.
Balance Patch 1 also improved tracking on Axatana light attacks, so launch-day impressions from before the patch can understate how cleanly it connects now.
Good Shell pairings
- Eredrim: fast Resolve generation plus strong punish windows after Shoulder Bash.
- Tiel: speed helps capitalize on short back-attack openings.
- Smert: high hit rate can support aggressive Resolve/stack plans outside Miracle.
Those are build directions, not hard restrictions. Any Shell can equip the weapon.