Don’t Give it a berry because when I did and steal an egg after that I tried to kill it but it turned invincible please let the creators know so you can still hurt a creature when there not fully tamed.
Me and my tribe love our lystro. They honestly don’t have any use to us anymore as we have all maxed our levels. But these critters are certainly a nice form of company. To tame them you can take some mejo berries. I believe aquatic mushrooms may work too if you are on aberration.