I’d argue that, especially when talking about Chakra gates, you can’t really practice to open them at all. You unlock them through certain prerequisites that have to be met. So when they are talking about „mastering“ the eight gate they probably mean unlocking it. Once you unlocked it you have the full control over it just as you can move your arms without needing to think about it. The process of finding out about them is one of those prerequisites I guess. However this is not based on a huge number of in lore facts and more on how other settings handle it.

This is the type of question you would ask about the reaper death seal

A hyuga’s byakugan can see the gates

@Silver789

Well Reaper Death Seal would only kill the user if they actually sealed something/someone. I dont think simoly summoning the reaper would get one killed.

As for the 8th Gate, no one really "masters" it, they simply learn how to open it. This doesnt necessarily mean that follow through with the action. The activation method seems simple enough.

Well, since seven of the eight gates are based on the chakra points in the buddhist religion, I am presuming that the eighth gate is pretty much the sum of all of them together. Also, considering how balance is a focal points for those chakra points, I think that mastering the balance throughout every chakra and throughout ones entire body simultaneously is, in escence, mastering the eight gate. Hopefully this helps answer your question