Cheapest priced copy (Commander Legends: Battle for Baldur's Gate): $0.35 at Card Kingdom, near mint, their price list as of .
Commander Liara Portyr 
Legendary Creature — Human Soldier · 5/3 · Uncommon · Commander Legends: Battle for Baldur's Gate · #270
Whenever you attack, spells you cast from exile this turn cost {X} less to cast, where X is the number of players being attacked. Exile the top X cards of your library. Until end of turn, you may cast spells from among those exiled cards.
Legal inCommanderLegacyVintage
Not legal inBrawlStandardPioneerModernPauper
4 printings · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Commander Legends: Battle for Baldur's Gate | 270 | Uncommon | $0.35 | $0.49 |
| Commander Legends: Battle for Baldur's Gate | 418 | Uncommon | $0.35 | $0.49 |
| Commander Legends: Battle for Baldur's Gate | 529 | Uncommon | — | — |
| The List | CLB-270 | Uncommon | — | — |
3 rulings from Wizards of the Coast
- 10 June 2022If you attack a planeswalker but don't also attack that planeswalker's controller, that player won't count toward the value of X.
- 10 June 2022Commander Liara Portyr's triggered ability reduces the cost of all spells you cast from exile, even if you are casting them with a different permission. For example, if you are casting an exiled permanent spell with an Adventure in the same turn that this triggered ability resolved, it would cost {X} less to cast.
- 10 June 2022Commander Liara Portyr doesn't have to be among the attacking creatures.