Cheapest priced copy (Morningtide): $4.99 at Card Kingdom, near mint, their price list as of .
Sigil Tracer 
Creature — Merfolk Wizard · 2/2 · Rare · Morningtide · #49
{1}{U}, Tap two untapped Wizards you control: Copy target instant or sorcery spell. You may choose new targets for the copy.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
1 printing · $4.99 to $24.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Morningtide | 49 | Rare | $4.99 | $24.99 |
4 rulings from Wizards of the Coast
- 1 April 2008If the spell is modal (that is, it says “choose one —” or “choose two —”), the choice of mode(s) can’t be changed.
- 1 April 2008Sigil Tracer’s ability can copy an instant or sorcery spell that isn’t targeted.
- 1 April 2008Since the activated ability doesn’t have a tap symbol in its cost, you can tap creatures (including Sigil Tracer itself) that haven’t been under your control since your most recent turn began to pay the cost.
- 1 April 2008If the controller of the original spell chose to pay an alternative cost (such as prowl) or an additional cost, that choice is also copied.