For years, Senshi fears that the Griffin meat soup that he ate when he is younger could be Dwarf flesh. When he eats the Griffin soup, it has a different taste which reinforces the possibility that he did ate dwarf meat. Then Laios uses the changeling mushrooms to turn a piece of Griffin meat into a Hippogriff meat. When Senshi eats the Hippogriff meat soup, it is the exact taste which meant that he did not eat Dwarf meat. Laios suspects that the dent on Senshi's helmet is result of a Hippogriff attack instead of a griffin attack as a Griffin attack will leave a claw mark instead of a dent.
