Easy:
At the start of the turn applies -3/-3 to all your monsters.
Electric: Tropix(Mega), Cubix(Mega), Mamvolt(Leg), Porkix(Epic), Electric Emblem
Fire: Chef Ashy(Mega), Sharkire(Epic)
Dragon: Evolon(Mega), Drach(Leg), Cockatrice(Rare)
Universal: Abyss Portal(Epic)
Medium:
At the start of the turn applies -3/-3 to all your monsters.
Hard:
At the start of the turn applies -5/-5 to all your monsters.
Expert:
At the start of the turn applies -5/-5 to all your monsters.
Fire: Flamite(Mega), Chef Ashy(Mega), Dark Suri(Leg), Ichire(Leg), Sharkire(Epic), Fire Emblem
Dragon: Evolon(Mega), Demon Draku(Mega), Rokuon(Epic), Cockatrice(Rare), Dragon Emblem
Electric: Cubix(Mega), Tropix(Mega), Batix(Leg), Mamvolt(Leg), Porkix(Epic) Electric Emblem
Universal: Abaddonus(Mega), Dark Portal(Mega)