Cheapest priced copy (Zendikar Rising): $0.35 at Card Kingdom, near mint, their price list as of .
Drana's Silencer 
Creature — Vampire Rogue · 3/2 · Common · Zendikar Rising · #99
When this creature enters, target creature an opponent controls gets -X/-X until end of turn, where X is the number of creatures in your party. (Your party consists of up to one each of Cleric, Rogue, Warrior, and Wizard.)
Legal inCommanderPioneerModernLegacyVintagePauper
Not legal inBrawlStandard
1 printing · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Zendikar Rising | 99 | Common | $0.35 | $0.49 |
5 rulings from Wizards of the Coast
- 25 September 2020To determine "the number of creatures in your party," check whether you control a Cleric, whether you control a Rogue, whether you control a Warrior, and whether you control a Wizard. The number is the total number of those checks to which you answered yes. Each creature you control can be counted for only one of those checks.
- 25 September 2020If an ability of a creature counts the number of creatures in your party, that number is counted as the ability resolves. If that creature is still on the battlefield when the ability resolves, it'll be counted if appropriate.
- 25 September 2020If a creature has more than one party creature type, and there are multiple ways to count that creature that could result in a different number of creatures in your party, the highest such number is used. For example, if you control a Cleric and a Cleric Wizard, the number of creatures in your party is two. You can't choose to have it be just one by counting the Cleric Wizard first as a Cleric.
- 25 September 2020An ability referring to the number of creatures in your party gets a number from zero to four. Such abilities never ask which creatures are in your party, and you never have to designate specific creatures as being in your party. You can't choose to exclude creatures from this count to lower the number.
- 25 September 2020The value of X is determined only as Drana's Silencer's ability resolves. Once that happens, the value of X won't change later in the turn even if the number of creatures in your party changes.