Cheapest priced copy (Ravnica Remastered): $0.35 at Card Kingdom, near mint, their price list as of .
Siege of Towers 
Sorcery · Rare · Guildpact · #76
Replicate {1}{R} (When you cast this spell, copy it for each time you paid its replicate cost. You may choose new targets for the copies.)
Target Mountain becomes a 3/1 creature. It's still a land.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
3 printings · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Guildpact | 76 | Rare | $0.49 | $0.49 |
| The List | GPT-76 | Rare | $0.49 | — |
| Ravnica Remastered | 123 | Uncommon | $0.35 | $0.49 |
4 rulings from Wizards of the Coast
- 1 February 2006The Mountain will remain a creature for the rest of the game. It doesn't have a creature type.
- 1 August 2008A noncreature permanent that turns into a creature can attack, and its {T} abilities can be activated, only if its controller has continuously controlled that permanent since the beginning of their most recent turn. It doesn't matter how long the permanent has been a creature.
- 12 January 2024As the replicate triggered ability resolves, you'll copy Shattering Spree for each time you paid its replicate cost, even if the original spell is no longer on the stack at that time (perhaps because it was countered).
- 12 January 2024The copies that replicate creates are created on the stack, so they're not "cast." Abilities that trigger when a player casts a spell won't trigger.