Sylas could imagine that from Lucius' perspective, things had spun too far out of control.
What he wanted to know now was just how much unilateral control Lucius had over the situation?
Right now, it could be said that he wasn't truly facing off against the Grimblades, but rather Lucius himself. That said, they weren't necessarily mutually exclusive.
For example, Archibald was a huge boon to Lucius, and the latter was clearly using him now. However, the appearance of Archibald had also allowed Lucius to be rewarded by the Grimblades… at least from what Sylas had deduced.
So where was the line, exactly?
The Grimblades would certainly also be aware of his feats, so how far would they allow Lucius to go?