I couldn't finish 'em. Looks like this's gonna get complicated.
The Dark Bat is an enemy from Final Fantasy Crystal Chronicles: Ring of Fates.
For this reason alone, they should be dealt with immediately to avoid being hit by Paralysis, or by having equipment that helps resist Lightning damage and/or prevents Paralysis. The player can fight them in the same manner as the Bat and Fire Bat; either wait for them to come to ground level to use ground attacks (happens less often due to them opting to use Thundaga), use aerial attacks to damage them, or grab onto them to attack them once then get off, as they are quick to counter being grabbed onto.
As with most enemies in Shadowland, and some enemies in the Crystal Temple, using either a Cure spell, Clear spell, Potion, or Ether on or near the enemy will make them non-transparent, increasing the amount of damage they take and making it easier to see where they are.
Of note, Dark Bat has a -5 weakness to Holy elemental attacks.