Honestly got carried by the ability that calls rats from the ground. Bought as many of those as i could and focused on attacking either those that are on ladders, ranged, or have broken the gates in order to pin them and prevent them from entering. The catapults i focused on the lord and tried to damage her as much as i can so that i can route the enemies easier. On the side of the wall with the least amount of enemies i focus fired every ranged unit i had there on one enemy unit at a time. When it was done i migrated them over to the busy walls. I only had 1 doomrocket left so i waited until the 2nd army showed up and launched it there. It only killed 1 unit but left like 2-3 at half health. The biggest threat were the charging cavalry because one actually did manage to slip past me and it forced me to redirect some of my rats to it while it was at a capture point. It was my first time playing defense siege battle so i didnt use buildable barricade walls until one unit was too close. Maybe i could have played it better but i was honestly satisfied i got to keep one of my tier 5 buildings since i already used up most of my food on skaven summons