Okay, I did it with this party:
But I have lost a half of my servants (Georgios, Siegfried, Lancelot) to eliminate all enemies... tbh, I could done it much more easier and faster if I just killed Caesar instead of Astrea, but I just wanted to eliminate all enemy servants so, that is. As the result I literally lost two servants in fight with Astrea (who was the last enemy servant)...
But, still at the end of the day wis is the win... so I kinda did it.