Rey no longer had any [Binding], [Mind Control], or [Domination] Skill at his disposal, so it would be very difficult to get a Summon under his Control.
Using Summoning Magic and controlling the Summons was still within his power—especially Elementals—but Beasts were completely different.
Beasts came from another world, and unlike Monsters who had flesh as their bodies and Mana Cores as hearts, or Elementals who were primarily composed of natural elemental attributes and had some kind of core that functioned as a stabilizer, the Beasts were fully composed of Mana—flesh, core, and all.
They might seem like physical bodies, but ultimately they were simply Mana given form.
Casting Magic to control them wouldn't work at all.
"I guess this is where the difference between Skills and Magic come into play once again…" Rey chuckled as he heard Ater's explanation.
"Precisely!"