Eris, Roar of the Storm
Legendary Creature — Elemental Warlock
This spell costs 
less to cast for each different mana value among instant and sorcery cards in your graveyard.
Flying, prowess, prowess
Whenever you cast your second spell each turn, create a 4/4 red Dragon Elemental creature token with flying and prowess. and prowess.
Aurore Folny
Rulings
The mana value of a split card in the graveyard is the total mana value of both halves of that card. It does not have two mana values.
(wotc • 2024-04-12)
Spells that were cast before Eris entered the battlefield count. If Eris was the first spell you cast this turn, the next spell you cast this turn is your second spell.
(wotc • 2024-04-12)
The mana value of a double-faced card in your graveyard is always the mana value of the front face.
(wotc • 2024-04-12)
If the mana cost of a card in your graveyard includes {X}, X is 0 for the purpose of determining its mana value.
(wotc • 2024-04-12)
Related Cards
Printings
Rulings
The mana value of a split card in the graveyard is the total mana value of both halves of that card. It does not have two mana values.
(wotc • 2024-04-12)
Spells that were cast before Eris entered the battlefield count. If Eris was the first spell you cast this turn, the next spell you cast this turn is your second spell.
(wotc • 2024-04-12)
The mana value of a double-faced card in your graveyard is always the mana value of the front face.
(wotc • 2024-04-12)
If the mana cost of a card in your graveyard includes {X}, X is 0 for the purpose of determining its mana value.
(wotc • 2024-04-12)