I was playing a casual 2v2 game with AI allies and enemies when I decided to try the Last Man Standing option. It was a hard AI game, but I managed to get late game advantage after grabbing 4/5 relics. As we were defeating the second enemy, I turned against my ally and cast a swarm of units on their main TC, causing them to resign. I decided to try again with a megarandom map and sudden death mode. My ally and I were Mongols and Bohemians, respectively. I focused on relic grabbing and building castles while my ally did most of the skirmishing. I rejected an alliance proposal from a low-scoring enemy AI to avoid betraying my ally. However, I failed to notice that my ally had turned against me until they were already in my town with an army of wagons, pikemen, and rams. My units failed to attack and my buildings were falling, as I realized my diplomacy with my ally was still set to ally. I tried to defend, but it was too late, and I was defeated.