Cheapest priced copy (Secrets of Strixhaven Commander): $0.49 at Card Kingdom, near mint, their price list as of .
Lattice Library 
Enchantment · Rare · Secrets of Strixhaven Commander · #40
This enchantment enters with X study counters on it.
When this enchantment enters and whenever you cast your first spell with {X} in its mana cost each turn, create a 0/0 green and blue Fractal creature token. Put a number of +1/+1 counters on it equal to the number of study counters on this enchantment.
Legal inCommanderLegacyVintage
Not legal inBrawlStandardPioneerModernPauper
2 printings · $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Secrets of Strixhaven Commander | 40 | Rare | $0.49 | — |
| Secrets of Strixhaven Commander | 88 | Rare | $0.49 | — |
2 rulings from Wizards of the Coast
- 20 March 2026If you cast your first spell with {X} in its mana cost during a turn before Lattice Library is on the battlefield (including Lattice Library itself), casting another spell with {X} in its mana cost later in the turn won't cause its last ability to trigger.
- 20 March 2026Lattice Library's last ability resolves before the spell that caused it to trigger. It resolves even if that spell is countered or otherwise leaves the stack.