Adaptive Blade

The Adaptive Blade is an Dungeon Sword that can be obtained from Floor 2 of The Catacombs. You will also get one after defeating the Floor 2 boss, Scarf, 150 times from the Scarf Collection. As the lore suggests, the weapon has special stats based on the chosen class ability.
 * Berserk: +35, +5
 * Healer: +20% regeneration and Restore +5 HP/s to nearby allies
 * Mage: +200
 * Tank: +100  +5
 * Archer: +100

The Archer has the worst out of all the special class abilities due to the fact that the +100 doesn't retain when switched to a bow.

* Assuming you have the Berserker class. It is not confirmed yet whether the bonus of abilities do also get affected by the Catacombs level or not.

** Base stats 170. Dungeoneering leveling is not included.

Trivia

 * The Adaptive Blade doesn't have built-in or.
 * The Adaptive Blade is the first and one of four custom stone swords currently added to the game, the others being the Earth Shard, the Wither Cloak Sword and the Fel Sword.
 * The Adaptive Blade was created along Adaptive Armor, which was likely based from League Of Legends's (removed, old) Adaptive Armor mastery and Adaptive Helm.
 * It is not recommended to buy this item from the post-boss chest, as it is usually cheaper from the auction house. However, one could also kill Scarf 150 times as this item is also available in Scarf Collection IV.