Power Surge (Retro) [30th Anniversary Edition] Cat Beast Set: March of the Machine:

Set: March of the Machine: The Aftermath Type: Legendary Creature — Kor Artificer Rarity: Mythic Cost: {4}{R}{W} Affinity for Equipment

there is an additional combat phase followed by an additional main phase

convert Prowl

Set: 30th Anniversary Edition Type: Instant Rarity: Rare Cost: {U} Change the text of target spell or permanent by replacing all instances of one color word with another

Supporting this hteory

Power Surge (Retro) [30th Anniversary Edition] Cat Beast Set: March of the Machine:Set: 30th Anniversary Edition Type: Enchantment Rarity: Rare Cost: {R}{R} At the beginning of each player's upkeep, Power Surge deals X damage to that player, where X is the number of untapped lands they controlled at the beginning of this turn.