Four of these combine to form a single adversary. This foe shouldn't be a problem for a strong party.
At times it will appear to attack alone, but will in fact attack in groups of four, with the four sprites overlaid over each other so only one appears on the screen. They are not very dangerous, and are vulnerable to Ice and Water-elemental spells like Blizzaga and Flood.
The only thing to note is that Vector Lythos's Petrify vulnerability cannot be exploited with Stoneblade, since it also has Death protection that makes it immune to Break. Aside from this, it is easily beaten.
1st Turn: Attack (100%)
2nd Turn: Attack (33%) or Fireball (33%) or Bite (33%)
1st Turn: Attack (33%) or Tusk (33%) or White Wind (33%)