The Chosen Ones

Well, so there's an otherone, but it requires some more work:

~~~~~~~~~ ~~~~~~~~~~~~~ IDEA ONE ~~~~~~~~~~~ ~~~~~~~~~~~

Make 4 pillars in the corner of boss' room. Every X% hp he (the boss) loses 1 random tower gets pumped up. That could be translated with Gives positive auras to the boss, gives negative auras to the heroes.
So like, you can make 1 tower about hp rege, 1 about attack speed etc. You may not make towers but something else, i just suggest towers it is cooler .

The heroes can fight them, or ignore them, If the tower gets destroyed the auras it produced are swiped away. You can add visuals on it and whatnot.

Now an other one:

~~~~~~~~~~~ ~~~~~~~~~~~ IDEA TWO ~~~~~~~~~~~ ~~~~~~~~~~~

The lightning Esper, (name), Has learnt to manipulate lightning in its very pure form. He throws wave of lightning (small radius) everywhere around him. (like 5 small waves.) The waves then start bouncing, if a wave touches and other an explosion is triggered.