He only needed to make sure that Profound Sage Tyrannical Song was really only at the Fourth Stage Realm. As for the rest, he could simply leave that to Young Master Hai.

His junior brother was about to be possessed by an inner demon due to this 'Profound Sage Tyrannical Song'. Therefore, as long as he found out that Profound Sage Tyrannical Song was actually only at the Fourth Stage, he would be able to overcome these demons.

Once Young Master Hai transcended his tribulation and reached the Fifth Stage, he would then be able to challenge Profound Sage Tyrannical Song and deal with the karmic ties that they had!

As for whether Profound Sage Tyrannical Song had any trump cards, it was no longer something that he had to bother himself with. With Young Master Hai's intellect, he would certainly be able to speculate about such things.

...Demon Monarch Mad Tyrant had yet to see the latest news posted by the Daily Cultivator, so he did not know about Profound Sage Tyrannical Song beating