How to Get Treespear - Elden Ring
It can be found on one of the Carriages beside stormveil castle.
You can take the hidden path on the broken bridge to get to Liurnia without clearing Stormveil castle.
After reaching Liurnia look at the bottom of the cliff, you will see platforms that you can jump on to get to the bottom safely.
Once you reach the bottom, just follow the path southeast and you will see a broken carriage that is guarded by a giant.
If your level is too low, you can just run past him and go straight to the carriage and open the chest containing the treespear.
The Treespear has the skill called sacred order, it imbues the weapon with holy damage and will give additional faith scaling damage.
It has a unique charged attack that pierces the enemy twice.
The weapon scales with strength, dexterity, and faith but leans on dexterity more than the standard.