Question how to do a sculpt obsion in unity game

i want to do a sculpt game in unity and I want to do a sculpting like sculpting mode in blender, how to do that?

 

It's quite difficult. As a general answer, you'll do it with procedural mesh generation (google it, and look in particular for the Catlike Coding tutorials, which are very good). Then you'll probably need to dig into the literature and find some good algorithms for blob sculpting.