There is indeed some methods of magic used by both AI and player. You can't really do things like cast fire out of your hand or create magic shields, but there's the powers you unlock from bosses such as temporarily increasing your stamina, chopping trees faster, increasing your damage, etc. Other than these powers, you can't really do things like casting magic attacks or healing. I think the gameplay focus on Valheim is more into grounded things like traditional melee combat, bow shooting, etc.