101Leafy researched the games.
Upper Battleaxe

The interior of this one handed Axe is a dreadfully potent poison factory.
| Class | Sword |
|---|---|
| Rarity | 4 |
| Attack | 224 |
| Poison | 300 |
| Slots | 0 |
| Price | 3,810z |
Upgrades
| Upgraded from | Poison Battleaxe |
|---|---|
| Upgrades into | Deadly Battleaxe, Dual Battleaxe |
Upgrade tree from モンスターハンターポータブル 2nd G 公式ガイドブック (Enterbrain, 2008), page 700.