Your Constitutioin score increases by 2, and your Wisdom score increases by 1.

There are no records of how old Kelpies can get, depending on the amount of sunlight they can get and the water quality their age can vary imensly.

Their often cruel treatment tends to shove many kelpie into an evil mentality, but many can overcome it. Evil or not, a general distrust of society as a result of a toxic climate tilts most kelpies towards neutral or chaotic alignments.

Depending on the shape the Kelpie is currently in the size may vary. But it's size is medium.

Your base walking speed is 40 feet and swimming speed 20ft.

Your creature type is plant, rather than humanoid.

Your hooves are natural melee weapons, which you can use to make unarmed strikes. If you hit with them, you deal bludgeoning damage equal to 1d4 + your Strength modifier, instead of the bludgeoning damage normal for an unarmed strike.

You count as one size larger when determining your carrying capacity and the weight you can push or drag.

In addition, any climb that requires hands and feet is especially difficult for you because of your equine legs. When you make such a climb, each foot of movement costs you 4 extra feet, instead of the normal 1 extra foot.

Being a hunter you can see fairly well in the dark. You can see in total darkness within 60 feet of you as if it were bright light. You can’t discern color in darkness, only shades of gray.

As a kelpie, you can shift between your human, centaur, and horse form twice per short rest. The spell lasts about 12 hours before you revert to centaur form. 

You can speak, read, and write Common and Sylvan.