Cheapest priced copy (Ravnica Allegiance): $0.49 at Card Kingdom, near mint, their price list as of .
Lumbering Battlement 
Creature — Beast · 4/5 · Rare · Ravnica Allegiance · #15
Vigilance
When this creature enters, exile any number of other nontoken creatures you control until it leaves the battlefield.
This creature gets +2/+2 for each card exiled with it.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
2 printings · $0.49 to $0.79 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Ravnica Allegiance Promos | 15s | Rare | — | $0.69 |
| Ravnica Allegiance | 15 | Rare | $0.49 | $0.79 |
3 rulings from Wizards of the Coast
- 25 January 2019If a card you chose to exile leaves exile or somehow never moved to the exile zone in the first place, Lumbering Battlement doesn't get +2/+2 for that card.
- 25 January 2019Auras attached to the exiled creatures will be put into their owners' graveyards. Any Equipment will become unattached and remain on the battlefield. Any counters on the exiled creatures will cease to exist. When the cards return to the battlefield, they will be new objects with no connection to the cards that were exiled.
- 25 January 2019If Lumbering Battlement leaves the battlefield before its triggered ability resolves, you can't exile any nontoken creatures.