Volo's Guide to Monsters pg 157
The grung is a 9th-level spellcaster. Its spellcating ability is Wisdom (spell save DC 12, +4 to hit 1d20+4 with spell attacks). It knows the following ranger spells:
1st level (4 slots): cure wounds, jumpAmphibious. The grung can breathe air and water.
Poisonous Skin. Any creature that grapples the grung or otherwise comes into direct contact with the grung's skin must succeed on a DC 12 Constitution saving throw or become poisoned for 1 minute. A poisoned creature no longer in direct contact with the grung can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.
Grung poison loses its potency 1 minute after being removed from a grung. A similar breakdown occurs if the grung dies.
A creature poisoned by a grung can suffer an additional effect that varies depending on the grung's skin color. This effect lasts until the creature is no longer poisoned by the grung.
Green. The poisoned creature can't move except to climb or make standing jumps. If the creature is flying, it can't take any actions or reactions unless it lands.Standing Leap. The grung's long jump is up to 25 feet and its high jump is up to 15 feet, with or without a running start.
Dagger. Melee or Ranged Weapon Attack: +5 to hit 1d20+5 , reach 5ft. or range 20/60 ft., one target. Hit: 5 1d4+3 piercing damage, and the target must succeed on a DC 12 Constituion saving throw or take 5 2d4 poison damage.
Shortbow. Ranged Weapon Attack: +5 to hit 1d20+5 , range 80/320 ft., one target. Hit: 6 1d6+3 piercing damage, and the target must succeed on a DC 12 Constitution saving throw or take 5 2d4 poison damage.
Rain Forest, Tropical Jungles