Riverchurn Monument pm19 Whenever Festerleech deals combat damage

Whenever Festerleech deals combat damage to a player

you may exile one of those creatures

That player may search their library for a basic land card

Creatures and enchantments you control have "Spells your opponents cast that target this permanent cost {1} more to cast

Fire Prophecy deals 3 damage to target creature

Riverchurn Monument pm19 Whenever Festerleech deals combat damage{1}, {T}: Any number of target players each mill two cards. (Each of them puts the top two cards of their library into their graveyard.) Exhaust {2}{U}{U}, {T}: Any number of target players each mill cards equal to the number of cards in their graveyard. (Activate each exhaust ability only once.)