Flying Eyeball

Special Ability
When evolved into an adventurer, Flying Eyeball will receive double Dungeon Level XP. Equipping an Ego Sword (or tier equivalent) or Gram will remove this bonus.

Even though Flying Eyeball is an adventurer specialist, it is designed to be a dungeon pet. While in dungeons, it will not attack. Instead, it will "mark" the enemy with the lowest max HP and cause all other pets to target the marked pet. It will mark another enemy once the previous marked enemy dies. Mage attacks and other multi-target pet attacks will all focus on the marked enemy instead of being spread out like normal. This is useful for quickly killing enemies that can summon backup or for killing the Mirrors in Neutral/Elemental Infinity Tower. Marked enemies will also take 10% + ¼CL% damage, maxing at 35% at CL 100

Eyeball benefits from being geared toward Speed, so it will mark the enemy before your other pets attack. Since Eyeball itself does not attack, don't worry about gearing for Attack.

Puting Eyeball into your challenge-team helps with the evo-condition.