I'm just need to clear up impervious. Against what powers does it not come into play? Splash damage from EE or pulse wave? Does poison work against it?

Anything that doesn't require an attack roll or doesn't target a figure so Poison will bypass it as will Pulsewave (when more than 1 fig is affected), Psychic Blast accompanied attacks, Force Blast, Outwit, Plasticity, Mystics ability, Perplex, Probability Control

Any powers that do not actually target the figure.

Splash damage from EE.
Poison
Force Blast
practically any attack with Psychic Blast.
Mastermind
Mystics team ability

There are a few of the things that Impervious has no affect against.