Cheapest priced copy (Innistrad: Double Feature): $0.35 at Card Kingdom, near mint, their price list as of .
Harvesttide Sentry 
Creature — Human Warrior · 3/1 · Common · Innistrad: Midnight Hunt · #186
Coven — At the beginning of combat on your turn, if you control three or more creatures with different powers, this creature can't be blocked by creatures with power 2 or less this turn.
Legal inCommanderPioneerModernLegacyVintagePauper
Not legal inBrawlStandard
2 printings · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Innistrad: Double Feature | 186 | Common | $0.35 | $0.49 |
| Innistrad: Midnight Hunt | 186 | Common | $0.35 | $0.49 |
6 rulings from Wizards of the Coast
- 24 September 2021The blocking restriction is applied only when blockers are declared. After the coven ability resolves, if a player blocks Harvesttide Sentry with a creature with power greater than 2, reducing that creature's power won't make Harvesttide Sentry unblocked.
- 24 September 2021Harvesttide Sentry's triggered ability checks your creatures' powers both when it triggers and as it tries to resolve. If you somehow don't have enough creatures with different powers as it tries to resolve, nothing happens and Harvesttide Sentry can be blocked as normal.
- 24 September 2021Once its ability resolves, removing one of the creatures with different powers won't allow a player to block Harvesttide Sentry with creatures with power 2 or less.
- 24 September 2021Many coven abilities, such as that of Dawnhart Wardens above, are triggered abilities with intervening if clauses. You must control three or more creatures with different powers at the time the ability triggers and at the time the ability tries to resolve. They do not, however, need to be the same set of creatures in both cases.
- 24 September 2021A creature has different power from another if their powers are different numbers. For example, a 1/1 creature and a 2/1 creature have different powers.
- 24 September 2021For three creatures to have different powers from one another, each of their powers needs to be different. A 1/1 creature, a 2/1 creature, and another 2/1 creature aren't three creatures with different powers, even though both 2/1 creatures have different power than the 1/1 creature.