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.)Thundering Falls combines blue and red mana with a small but useful selection effect. It enters tapped and surveils one when it enters, letting you keep the top card of your library there or put it into your graveyard. Its Island and Mountain types make it searchable by effects that look for either type, giving it utility beyond an ordinary tapped dual land.
Blue-red spellslinger decks can use the surveil to send a spell with flashback or another graveyard use to the graveyard. Underworld Breach strategies also appreciate stocking that zone while fixing mana. If the next card is a useful piece of interaction, leaving it on top preserves the draw instead. The land supports selection and setup rather than directly increasing the number of cards in your hand.
Scalding Tarn can find it, allowing you to choose this land when the filtering is worth the delayed mana. Fetching it during an opponent's end step is often convenient because you can untap it on your next turn. A fetch land does not remove its tapped-entry requirement, so finding it during your own main phase will not normally provide immediate mana.
Plan opening land sequences around that delay. Use an early turn when you do not need to cast a spell, or choose a different searchable land when interaction must remain available. The land is most useful when its two colors, basic land types, and graveyard-aware filtering all support the deck, rather than when the mana base simply needs another dual land.
