Hardcore

Hardcore is a mode that will make your head spin. I can't recommend trying to use this mode to grind. The reward isn't really worth it. Get at least mech or thomas or korean man to actually beat it. You can solo it if you have these towers but will die at the boss.(Same HP, way faster movement speed). Get some extra people to help you beat this.

Tips

Remember how I said that you should use mech, thomas, and korean man to beat this stage? Well those things cost a fortune to place down. You can't farm, so try to get something to cover you, like ak 47 (though he also costs a fortune).

Out of all 3 summoner towers, I recommend mech the most. He can tank all the lighting smalls at wave 30. I recommend thomas the least. He is cheaper than mech but can't even attack. He has the same spawn interval as mech, but at at max mech actually spawns 2 times faster.

Use temple, it's the only tower that isn't a summoner i recommend. His damage is insane at max and cost significantly cheaper than thomas and mech. It can 1 shot all those lightning small and kill the metal in 2 hits.