So the boss(I will not even try to spell his name) stomps the ground every time he loses 30%(of maximum) hp.The stomp shouldn't deal much dmg but should give the buff Cristal's Shatterring(I misspelled that).Also the stomp's radius must be small , like a AOE of 300-500.
The units affected with the buff cannot move, cast spells or attack.They can be awakened from this "sleep" state if they are attacked or targetted by a spell 5 times.The boss will not intend to attack them , so the player must attack them itself.Everytime the buffed unit is attacked or targetted the boss recives some bonus , permanent and also stackable dmg.
If all the 3 dragon slayers are getting buffed , then the boss will start casting some kind of spell(that takes 30 sec 2 cast).The dragon slayers 's single escape is if they use spell books or they're(alive) summons.After 30 seconds , the buff will fade and the boss will recive bonus damage equal 30 attacks/target of buffed units.
IDEEA:If you decide to use my entry , aero , make the basic dmg of the boss low at start , otherwise it'l get too imba.