Elders' help
Other than the Warrior Enlightenment Potion's effect, Michael started to notice the effects a combination of specialized body refinement techniques, Energy Nourishing Pills, and Body Strengthening Pills had on his Summons.
The Archer's Agility and Dexterity increased as they completed the first stage of their body refinement technique. They grew more nimble and were able to release arrows much faster than before without affecting their accuracy.
The Knights, on the other hand, used body refinement techniques that enhanced their endurance and stamina to act as the guardian protecting everyone at the frontlines. Contrary to them, the Berserkers' focus was raw physical strength. As long as they could hit hard enough to eliminate their enemy with a single strike, nobody would be able to harm them!