Tree wells can be your friend and provide shelter but has the potential to kill you, usually by suffocation.
Tree wells can get quite deep and most people accidently falling in usually go in head first. Skiing, boarding, snowshoeing around trees beware of collapsing edges where you'll also bring down a mass of snow on you.
On the plus side they make a great shelter if you are aware of them. Ideally come at it from the downhill side digging uphill but make sure the trench in has an L or T shape to stop/reduce the wind coming in.
I've never had any luck at building an igloo it takes forever and pretty much looks like it was done by a drunk 3 legged pig 😲. A tree well shelter is pretty much a snow cave half built.