Cheapest priced copy (Time Spiral Remastered): $1.99 at Card Kingdom, near mint, their price list as of .
Nether Traitor 
Creature — Spirit · 1/1 · Rare · Time Spiral · #120
Haste
Shadow (This creature can block or be blocked by only creatures with shadow.)
Whenever another creature is put into your graveyard from the battlefield, you may pay {B}. If you do, return this card from your graveyard to the battlefield.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
3 printings · $1.99 to $54.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Secrets of Strixhaven Commander | 220 | Rare | $2.29 | — |
| Time Spiral | 120 | Rare | $3.99 | $54.99 |
| Time Spiral Remastered | 127 | Rare | $1.99 | $14.99 |
6 rulings from Wizards of the Coast
- 19 March 2021Once a creature has been blocked, that creature remains blocked and will deal and be dealt combat damage even if it gains or loses shadow or if the blocking creature gains or loses shadow.
- 19 March 2021Multiple instances of shadow on the same creature are redundant.
- 19 March 2021If multiple creatures are put into your graveyard at the same time, Nether Traitor's ability triggers for each of them. Once you return it to the battlefield, you may pay {B} for the other abilities as they resolve, but they'll have no effect if you do. Even if Nether Traitor returns to your graveyard, it's considered a new object and won't be returned.
- 19 March 2021A token you own that dies is put into your graveyard before it ceases to exist.
- 19 March 2021If an attacking creature has multiple evasion abilities, such as shadow and flying, a creature can block it only if that creature satisfies all of the appropriate evasion abilities.
- 19 March 2021If Nether Traitor and another creature are put into your graveyard at the same time, Nether Traitor's ability won't trigger. This is because it must be in your graveyard before the creature dies in order for its ability that returns it to the battlefield to trigger.