I am new to Descent, and playing the first campaign. When the Wrath comes into play, it says it "retaliates" after every hero attack. (I might have wording wrong) What does this mean exactly? I first thought it would get 4 attacks, 1 after each hero. But that seemed excessive. Thoughts?

Can you specify which game component you are referring to? What do you mean by "Wrath"? As far as I now, "retaliate" is no Descent game term. This is a mechanic present in Gloomhaven, though.