Cheapest priced copy (Foundations Jumpstart): $0.35 at Card Kingdom, near mint, their price list as of .
Wall of Lost Thoughts 
Creature — Wall · 0/4 · Uncommon · Foundations Jumpstart · #384
Defender (This creature can't attack.)
When this creature enters, target player mills four cards. (They put the top four cards of their library into their graveyard.)
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
3 printings · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Foundations Jumpstart | 384 | Uncommon | $0.35 | — |
| Jumpstart | 190 | Uncommon | $0.35 | — |
| Ravnica Allegiance | 59 | Uncommon | $0.35 | $0.49 |