Cheapest priced copy (Jumpstart 2022): $0.49 at Card Kingdom, near mint, their price list as of .
Swarm Shambler 
Creature — Fungus Beast · 0/0 · Rare · Zendikar Rising · #362
This creature enters with a +1/+1 counter on it.
Whenever a creature you control with a +1/+1 counter on it becomes the target of a spell an opponent controls, create a 1/1 green Insect creature token.
{1}, {T}: Put a +1/+1 counter on this creature.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
5 printings · $0.49 to $0.69 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Jumpstart 2022 | 734 | Rare | $0.49 | — |
| Zendikar Rising Promos | 207p | Rare | $0.49 | $0.49 |
| Zendikar Rising Promos | 207s | Rare | — | $0.69 |
| Zendikar Rising | 207 | Rare | $0.49 | $0.49 |
| Zendikar Rising | 362 | Rare | $0.49 | $0.49 |
4 rulings from Wizards of the Coast
- 25 September 2020If a spell targets a creature you control with a +1/+1 counter on it more than once, Swarm Shambler’s ability triggers only once.
- 25 September 2020An ability that triggers when a creature becomes the target of a spell resolves before the spell that caused it to trigger. It resolves even if that spell is countered.
- 25 September 2020You create just one Insect token, no matter how many +1/+1 counters the target creature has on it.
- 25 September 2020If a creature without a +1/+1 counter on it becomes the target of a spell an opponent controls, putting a +1/+1 counter on it after that won’t cause Swarm Shambler’s middle ability to trigger.