There was still quite some distance between the spiritual guardian knights and Bruce. Moreover, since they were not under the range of the "faith" spiritual qi light ring, their attack powers were much weaker.
At the same time, the inferno knights were long-distance attackers. They weren't so much stronger in their close-range capabilities. So when they got close to the spiritual guardian knights, something of a stalemate was what resulted. On average, it would be two spiritual guardian knights against one inferno knight. That could only stall the inferno knight.
Still, Abel was more than satisfied with this. There was too much distance in terms of how the inferno knights could cast spells over proximity. If it weren't for the spiritual guardian knights, there was no way that he could easily cast any spells. With a wave of his hand, he activated one "aging" curse on Hephastos while commanding the eleven spiritual guardian wizards to assist in the offense.