Generally mutations are a good thing! People spend a lot of time and money trying to breed them because they're cute and valuable. They are rare, some more than others. Most of the time they don't have an effect on the lion. However, some mutations are lethal and will kill the lion, or the mutation will cover up how the lion looks which sometimes is a negative.
So to try and answer the question, yes, they are a good thing.

You have liked this post!

I suggest reading more about mutations on the wiki page: http://liodenwiki.wikidot.com
Go to the Breeding tab, and read all you like!
I assume the primal in your cave is the mutie you found? Congratulation! He's a beautiful lion!
If you want to see all the mutations, go to the lion wardrobe and try all the different mutations to see what they look like.
Hope I could help, and feel free to pm me with any more questions :)

You have liked this post!

Mutations (muties) are usually considered good because they're rarer than normal lions. Some muties such as hybrids and lethals can cost a lot. Your average mutie will usually cost more than your average lion.
Players usually have different reasons as to why they want a specific mutie, for some players, it's their goal.
Some mutations impact the lion others just have line art changes.
Some muties can also be kinged. Primals are a passable mutation so if kinged, it has a possibility to pass its mutation onto its cubs. Other passable mutations are piebalds and patches.
Some muties are rarer than others but I'm pretty sure all muties are rarer than non mutated lions.
Some people send muties to the tree hoping to give a pleasant surprise to whoever picks it up.

You have liked this post!