Ok.
1) Instead of the wall for the tesla towers to sit on use stone bridge. The towers will target even under them.
2) Make the stone bridge 5 long on each side with no gaps and have 5 full tesla towers on each side so 10 total. To make this happen I used all my coins on mithril / gold to make 10 towers.
3) Make the building the dwarves are standing in 7 squares wide.
4) Put stone bridges all across every 3 squares up for 3 levels.
5) Put catapults on these tiered stone bridges so 6 in total and a space between each side for a ladder all the way to the top.

6) Above the highest catapult cram 6 pet houses. The pets use the ladder to go heal assuming they survive a night.
7) make sure you are at least 5 squares down before you start base building under there. replace every square directly above your base with 5 layers of the hardest material you can afford. Once they in you base you dont get tesla help any more and they wont burn at dawn......
8) If you not making Tesla towers then prioritise weapons before armour.
9) FIll inside the building with doors 2 layers high. Dwarves are immune to melee in a door frame.
Every space under the tesla towers and as far out as the towers / catapults shoot put down stone fence. Reduces speed by 50% so catapoults hit and more shots on Tesla.
10 make the Fences submerged. Water slows mobs by 50% and stacks with fences so now they move at 25% speed.

Hope this helps.
Pixie

Nice design, but it's alot cheaper to just use 2 max tesla turrets (2 Steel Arrow turrets work too) on both sides and you should be able to last long enough to escape the world. Also it's surprising no guardians spawned, since you are level 13.

Nice design, but sorry friend. This won't survive endgame on harder difficulties.

do you call this invasion? LOL :) 10x more monster is an invasion, on hard, you cannot stand the attack ;)

im close to invasion im at level 10 just 2 more for the invasion

hehe thank you :) the mithril i got by exploring every little bit still uncovered on map. can be a real pain in the ****

near the end it sounds like the Chipmunks (ya know Alvin?) but overall interesting strategy and i might end up trying it great work, how u get all that mithril?

Yeah that can be a pain but if its more or less a straight shot from the portals to your traps they very rarely attack your walls. At which point you can rush out with some dwarves and finish those mobs off.

In my case, monsters tend to destroy de walls if the shortest path is that. I have to extend my walls or dig deeper to create my shelter