http://imgur.com/ZuhQh69
When I have Harynx use the decoy ability, it just adds an invisible tile that can't be walked on, and enemies won't target it even if it's in their attack range.
http://imgur.com/uqToDLL (the only evidence that it exists other than you can't move on the tile; it has 0/0 health)
Screencap with enemy's movement range: http://i.imgur.com/lbSuEiT.png
Edit: And when I attack the 'decoy' to try and remove it, I get this message: http://i.imgur.com/sPqtojk.png
This log should have the ability use in there
I can confirm this bug too. Used a decoy, energy went, tile became not passable, but no visuals were confirmed.
Thanks for the report! I fixed it--the fix will be in the next build. ;)