While attuned to this weapon you have advantage on saves against being poisoned. You also gain proficiency on nature checks.

When you hit a creature with a weapon attack you can expand a sneak attack die to cause a writhing mass of jagged gems to appear at the point of impact, and the target must succeed on a Strength saving throw or be restrained by the gems. A Large or larger creature has advantage on this saving throw.. While restrained the target takes 1d6 piercing damage at the start of each of its turns. A creature can use its action to break the gems freeing the creature.

gem growth
You stab the ground and in a 15ft radius, centered on you, sprouts hard spike like gemstones. The area becomes difficult terrain for the duration. When a creature(excluding you) moves into or within the area, it takes 2d4 piercing damage for every 5 feet it travels. Once this ability is used it can’t be used again for 24hrs.