Complete "Breaking Eggs to Make an Omelet" with premium content.
As you progress through the game and start to finalize your questing in Argos (just before lvl 30), you will receive a Challenge quest chain with the first challenge being called "Suicidal Tendencies" which requires you to hold out for 15min. Each quest, as usual, requires you to survive for 5min longer per quest, with the final quest (Breaking Eggs) requiring you to survive for 30.
When you start out, you will have 6 paths to your base and area to your immediate south which you'll want for resources. You'll want to wall up the north, NW, NE, SW, S and SE entrances to your little valley area (you should have seen this map before in Homer Run, among other quests). I double walled each entrance from the very first quest, but it wasn't really necessary until about the 3rd. You won't even see any siege engines until the 25min one but initially, having 2 walls will help while your walls are still weak. Wall up the entrances and spam Villagers and single, then double, triple, etc. stack towers on each entrance (the northern most only really needs 1 tower until the 25min one as this was where the rams came from for me, but that's it otherwise), making sure to level up to Age 2 and 3 immediately, and then work toward Age 4 while maintaining your walls and towers. If you have a library (Greek), grab the +25% building health ASAP and be sure to stay on top of leveling up your walls first, and then your towers. If you are turtle specced, these quests should require no Military. If not, build your best units from around the halfway point onward, particularly for the later quests. The most important tip is to just stay cool, they will come in masses and I recommend just making another wall instead of repairing any damaged ones (same with towers).
If this method is not working for the last one (it didn't for me because I got rushed from 2 random sides at the very beginning of each early attempt), move back your southern walls to the treeline just to the South of your town center. Make sure your walls go on the OUTSIDE of the woods though, or else the bad guys will just walk on through and kill you. So basically, only 4 walls instead of 6.
This quest is located in Argos and I was around level 35 at the time. Simply complete quests for King Diomedes and this mission will become available. It quite a challenging mission but very enjoyable. You have to defend your town centre for 30 minutes with wave after wave of enemies attacking you. Build loads of walls and fortress’s and your come out on top!