Chicken of the woods?
This is called a northern tooth fungi. Described as a parasite, it can weaken trees, causing them to break in high winds, however, that doesn't mean your tree is doomed. I have seen quite a few of these fungi this year and my own experience with them was that they didn't necessarily show up again. That being said, the size of the trunk makes me think your tree is fairly mature and it won't live forever. Here is a great guide on fungi where on page 45 you can find out more about the northern toothed fungus. Nice picture too! https://www.fs.fed.us/nrs/pubs/gtr/gtr_nrs79.pdf