Mana Worm

WARNING: When facing these creatures, it is vital to kill/disable them before they can hit you. With the exclusion of Evolution, who can restore herself by transforming, this creature's default attack will PERMANENTLY lower the target's mana, with no way of regaining the lost stats.

The SuckMana makes them dangerous as an enemy, but as an ally it's quite average. They can sacrifice max Mana to increase Magic, but they don't use it for anything. However, unlike Glow Worms, they only have two fixed skills. You can take advantage that and their 2.0 Mana Growth by getting them some other skills to turn them into mages. Otherwise, they can serve as tanks with their StrongManaDrain and Regenerating abilities, or as combat-capable Mana batteries with TransferMana or the Rare Essence Transference.

Note the ManaWorms dropped/produced are materials and need to be crafted into the consumable version.