The Quest of Isaac O'Connor [Unfinished]

As you move closer, one of the spirits notices you. Fear flashes across its face, and it throws up a barrier around the clearing. You are now trapped inside this barrier with these five spirits.

"Did you kill our friend?" says the spirit that created a barrier. "Did you come to kill us off?"

"What? No!" you say.

"Yeah? Prove it!"

What is your defense?