Cheapest priced copy (Ninth Edition): $29.99 at Card Kingdom, near mint, their price list as of .
Biorhythm 
Sorcery · Rare · Secret Lair Countdown · #58
Each player's life total becomes the number of creatures they control.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
4 printings · $29.99 to $149.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Ninth Edition | 231 | Rare | $29.99 | — |
| Ninth Edition | 231★ | Rare | — | $129.99 |
| Onslaught | 247 | Rare | $29.99 | $149.99 |
| Secret Lair Countdown | 58 | Rare | — | — |
2 rulings from Wizards of the Coast
- 4 October 2004If a player controls no creatures when this resolves, their life total will become zero and they will lose the game.
- 4 October 2004This spell causes the player to lose or gain enough life to change to the new life total.