Grootslang is a very large serpentine-like creature, long as the largest anaconda. He has green scales all over his body, and he typically wears a voodoo hat with rodent bones lining it, with two gemstones on it for Acid and Cyanide. As described in Mushussu's Beastiary, his fangs are said to be as long as elephant tusks.
Much of his personality can be summed up in three statements: cunning, cruel, and a fasination for Gemstones. He holds little care towards others, and enjoys leaving others in a doubtful state of mind. Grootslang has a street tone to his voice, and an almost playful attitude towards those he decides to mess with, and he's not above cheap tricks to get what he wants, including holding others hostage to get more gemstones. This is possibly referencing the information from Mushussu's beastiary.
He first physically appears in Beach City, over by Greg Universe, as he confronts him, claiming to be from Equus. He took the time to mess with him, calling him a terrible father for not being with Steven as much as he should, before going off into town. He went through town, not caring for who was seeing him, and he went right to Miroslaw's Jewelers, where he procceeded to straight up rob the place of all their jewels before being confronted by Discord. After a short chat, he got away from him by trapping him in his hat. He reappeared later that night with Acid and Cyanide, procceeding to confront Lars Barriga, destroying his item for the Potluck. He ended up leaving though when Garnet showed up.
He stayed elusive until the end of the season, after kidnapping Amethyst, Connie Maheswaran, and Steven Universe to be used as ransom for the Diamonds. He thought he successfully handle the ransom, and snapped them out of his hyponisis before realizing he had been tricked. On seeing this, he took them away quick, and once alone, he tried to remove Steven's gemstone, considering it just a piercing. during this Ammie was formed for the first time. Ammie activated his hat, and he ended up sucked of all his magic, turning back into a normal adder.
Grootslang has shown to be able to hypnotize people, though he only showed this once with Amethyst, Steven, and Connie.