If I think this is the first one ... for the end of the event I'll go insane
Anyway I did'nt see it on the wiki so here a usefull tip from the many attempt i did:
The attaker role gets switched at the start of the enemy turn with the servant behind ( Napoleon - Fionn, Fionn-Nero, Nero-Napoleon) when the servant of that role gets HP broke, immobilized ( stun, charm etc...) or deafeated.
Good luck with both lotto and exhibition quest .