Instant-speed removal for just one blue mana is clutch, and often well worth the price of leaving behind a vanilla 3/3 creature
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Not everyone was in love with the upkeep cost of Lord of the Pit, even though Fallen Empires Breeding Pit made the cost seem easier to maintain, Sengir Vampire was a simple power flyer and if you played your cards right, easily pumpable
Hopefully the parallels between spell mana and Treasure are clear at this point
Boxing Ring: Green has never been great at removing creatures, but a two-drop artifact that allows your creatures to fight enemy creatures and then create a treasure if they fought this turn is a decent way to help clear the way for your big stompy bodies to get through for combat damage
If youd like to see a more visual guide, check out the MTG Fetch Lands visual guide