Cheapest priced copy (Core Set 2020): $1.79 at Card Kingdom, near mint, their price list as of .
Atemsis, All-Seeing 
Legendary Creature — Sphinx · 4/5 · Rare · Core Set 2020 · #46
Flying
{2}{U}, {T}: Draw two cards, then discard a card.
Whenever Atemsis deals damage to an opponent, you may reveal your hand. If cards with at least six different mana values are revealed this way, that player loses the game.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
3 printings · $1.79 to $7.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Core Set 2020 | 46 | Rare | $1.79 | $3.99Out of stock |
| Core Set 2020 Promos | 46p | Rare | $1.99 | $7.99Out of stock |
| Core Set 2020 Promos | 46s | Rare | — | $5.49Out of stock |
4 rulings from Wizards of the Coast
- 12 July 2019Every Magic card has exactly one mana value. A card with no mana cost has a mana value of 0, and 0 can be one of the six mana values that count toward Atemsis's ability.
- 12 July 2019The mana value of a split card is determined by combining its two halves. For example, the mana value of Fire//Ice in your hand is 4.
- 12 July 2019If a card in your hand has {X} in its mana cost, the value of X is considered to be 0.
- 12 July 2019If an effect causes you to play with your hand revealed, you can still reveal your hand as Atemsis's last ability resolves. The ability works as normal.