(Note: if you experience any immense crippling performance issues, sorry man, i do not know how to fix them, if you do miraculously fix them i will be immensely thankful.) Rules: No OP stuff (of coarse.) No comically massive things. Make sure the damage type for attacks is correct. Please make sure that you are able to be damaged. You may be able to add new waves, and i guess you can add new enemies (depends tho).
I added Pete boneswurth, a glass canon skeleton that unleashes massive damage to all unholy entities, Firing devastating star storms and obliterating them with his Darkshard sword, at low health he will pray, causing a damaging aura of energy to surround him and destroy projectiles and heal him.