Build heavily inspired from Circle's PS build of this map, but repurposed for survival, check it out here --> https://dundefplanner.com/map.php?load=4997.
Black arrows denote mortar direction
Hint 3 is a small corner you can place your TB in and aim at North east core / hint 4
I run upper + TB wave 23 and then swap my upper a guardian summoner and sit on the hint 2 stack for wave 24. You could do a guardian summoner on each stack but i found it just lengthened my runs with no real benefit, tho could make it safer.
I'm not sure tbh if the healing aura is 100% needed but i do know my TB takes damage and doesn't die with it there.
Stats posted are just my stats, tbh I think most important thing is having a TB with enough range to TB both stacks (mine is 7.8k TB). Tdmg for elec auras is nice too
** if you DO NOT have the secret, i'd recommend removing one owl per stack. slower run but the elec auras put in a lot of work **