Illyrio mopatis timing

[willhunter52 0]

During the challenge phase if Targ player is going second can Illyrio be knelt to use his effects before the first player begins initiating their challenges?

[ktom 598]

Which one? There are three.

Assuming you mean the neutral one from the Core Set, the answer is yes. Before any challenges are initiated in the challenge phase, ALL players get the chance to trigger "Challenges" and "Any Phase" effects.