The full WBC3 campaign for TPC 0.8.9b. This was included in 0.8.9 but got renamed for 0.8.9a when it was updated. But the installer only adds the updated files for that campaign's directory, leaving things in a little bit of a mess. So here's the whole thing to correct everything.
As there seems to be a problem with The Fifth Horseman campaign that comes with 0.8.9, here's the full campaign updated for 0.8.9b. But please, please, please delete all saved game data that you might have for this campaign, found in My Documents / The Protectors / Saved Games. Just delete anything in there that has The Fifth Horseman in the file names. Note that this campaign is the Hero of Etheria campaign, but renamed. So you can delete that Hero of Etheria campaign from CustomCampaigns.
To install this, simply extract "The Fifth Horseman (WBC3)" folder from the zip folder and place it in The Protectors / CustomCampaigns folder - replacing anything that already exists in there.