(Round 61 onward of the Reckless Roc battleground using the Skull attack from Skeletal Steed)
Skull is neutral against fire.
Skull is neutral against xmas-nature.
Skull is neutral against dark-fire.
Skull is weak against service-earth.
Skull is weak against earth-fire.
Skull is weak against service.
Skull is neutral against egyptian.
Skull is strong against electric-water.
Skull is strong against treasure.
Skull is weak against dark-earth.
Skull is neutral against nature-fire.
Skull is strong against shamrock.
Skull is strong against electric-fire.
Seems like it is WEAK against service and earth.
and STRONG against electric, treasure and shamrock!
Now I definitely want to breed a Deadwing!