Ah. Well this does bring up a problem. I'm guessing that, with my bars disappearing, I should be getting a new bar in place to "throw" back the hammer? I'm getting nothing. I'll check my bags and see if the hammer is there, maybe I can toss the hammer back that way. If that isn't an option, maybe this is a limitation to Bartender?
The hammer is not actually an item, so it is not visible in your bags. Instead, it is a spell. It works in a similar fashion to controlling a vehicle. By default, your main bar (bar1) is setup to switch to show abilities of the vehicle you are currently possessing.
If your bar does change when you control vehicles, perhaps you didn't notice the spell when the hammer was thrown at you. It only gives you one button to press.
He will stun a random party member and throw his Hammer of the Righteous at them a couple of seconds after. If someone in your group can dispel the stun, you can throw back the hammer to Eadric and deal additional damage.
When your bars change, he most likely threw it at you. You need to throw it back at him.
I just tested it with only Bartender enabled and it does indeed work without taint. I turned back on my other addons to see what the taint log says and this is what I got.
8/14 03:48:08.100 An action was blocked in combat because of taint from TipTac - SetMultiCastSpell()
8/14 03:48:08.100 Interface\FrameXML\MultiCastActionBarFrame.lua:529 MultiCastFlyoutButton_OnClick()
8/14 03:48:08.100 MultiCastFlyoutButton3:OnClick()
8/14 03:48:11.164 An action was blocked in combat because of taint from TipTac - SetMultiCastSpell()
8/14 03:48:11.164 Interface\FrameXML\MultiCastActionBarFrame.lua:529 MultiCastFlyoutButton_OnClick()
8/14 03:48:11.164 MultiCastFlyoutButton3:OnClick()