What's the meaning of "He'll stay their wicked hand"

The song of The Last Rose of Cintra from the Netflix Witcher has the lines:

So seek ye now the White Wolf
He'll stay their wicked hand

What does it mean in the context of the song? I'm reading the meaning of the idiom but still not sure.
Do they mean that the witcher (White Wolf) will not be affected by madness of the "time of axe and sword"?

"Stay" is a synonym for "Stop" or "Halt" in this case. See defn 4a & 4b here:

https://www.merriam-webster.com/dictionary/stay

4a: to stop or delay the proceeding or advance of by or as if by interposing an obstacle : HALT
4b: to check the course of (something, such as a disease)

"their wicked hand" most likely means "their wicked intentions". To "stay someone's hand" means "to prevent them from doing what they were planning to do".

https://idioms.thefreedictionary.com/stay+someone%27s+hand#:~:text=stay%20(one's)%20hand,him%20from%20his%20role%20instead.

Most commonly (I think), this is done by persuasion rather than force. So you might stay someone's hand by saying "Wait, before you do that, have you thought about X?" for example.