Cheapest priced copy (Foundations Commander): $1.29 at Card Kingdom, near mint, their price list as of .
Sephara, Sky's Blade 
Legendary Creature — Angel · 7/7 · Rare · Commander Masters · #54
You may pay {W} and tap four untapped creatures you control with flying rather than pay this spell's mana cost.
Flying, lifelink
Other creatures you control with flying have indestructible. (Damage and effects that say "destroy" don't destroy them.)
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
8 printings · $1.29 to $11.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Commander Masters | 54 | Rare | $3.99 | $6.99 |
| Commander Masters | 471 | Rare | — | — |
| Foundations Commander | 47 | Rare | $1.29 | — |
| Core Set 2020 | 36 | Rare | $3.99 | $5.99 |
| The List | M20-36 | Rare | — | $6.49 |
| Core Set 2020 Promos | 36p | Rare | $4.99 | $8.99 |
| Core Set 2020 Promos | 36s | Rare | — | $11.99 |
| Starter Commander Decks | 33 | Rare | $3.99 | — |
3 rulings from Wizards of the Coast
- 12 July 2019Because damage remains marked on a creature until it's removed as the turn ends, lethal damage dealt to other creatures you control with flying may cause them to be destroyed if Sephara leaves the battlefield during that turn.
- 12 July 2019To pay Sephara's alternative cost, you may tap any untapped creatures you control with flying, including ones you haven't controlled continuously since the beginning of your most recent turn.
- 12 July 2019To determine the total cost of a spell, start with the mana cost or alternative cost you're paying (such as Sephara's alternative cost), add any cost increases, then apply any cost reductions. The mana value of the spell remains unchanged, no matter what the total cost to cast it was.