Arena
Land
{3}, {T}: Tap target creature you control and target creature of an opponent's choice they control. Those creatures fight each other. (Each deals damage equal to its power to the other.)
Joust
{1}{R}
Sorcery
Choose target creature you control and target creature you don't control. The creature you control gets +2/+1 until end of turn if it's a Knight. Then those creatures fight each other. (Each deals damage equal to its power to the other.)
Magus of the Arena
{4}{R}{R}
Creature -- Human Wizard
5/5
{3}, {T}: Tap target creature you control and target creature of an opponent's choice they control. Those creatures fight each other. (Each deals damage equal to its power to the other.)
Rivals' Duel
{3}{R}
Sorcery
Choose two target creatures that share no creature types. Those creatures fight each other. (Each deals damage equal to its power to the other.)