Adder Stone

While you carry this glassy stone, which has a natural hole in it and is the size of a small fruit, you have advantage on saving throws against effects that cause you to become paralyzed. These stones are often found near the place where a marra is slain. When the adder stone prevents someone from becoming paralyzed (one saving throw would fail and the other succeed), it shatters into worthless shards.

---added from Grim Hollow---