Deadly trial ideas for a player

One of my players are looking to undergo an ancient trial in order to grow more powerful. Having seen some of the great ideas on this sub, I was hoping for some concepts for trials of the Mind, Body & Soul.

This would be great if its combat, puzzles, anything like that!

​

Edit*

For further information, the concept is a trial for a specific PC however the rest of the party will be there to assist, so long as that PC succeeds on bringing back what is required the help is allowed. This ideally would span 2 or 3 sessions. They had pitched something similar to that of the Witcher trials, so I would like to try think of things that would test the Mind, Body and Soul.

e.g.

Combat to retrieve a rare ingredient or organ from a dangerous creature

some form of survival skill challenge as the final stage to survive the ancient process.

The players are around Level 11 and this trial is meant to be a very deadly affair, so any wild or dangerous ideas would be greatly appreciated!

Thanks you!