Solo players will be able to play the entire game by themselves. There will not be any bosses that will require a group. 
Players can set up barricades or structures to keep out Bound or other creature attacks. Players can then attack the Bound from a safe distance using ranged weapons.
Humans lack innate magical abilities, spells need to be tethered to a weapon or tool crafted in the realms. Using the spells will use up some of the durability. 
Armour and Protection
Armour in the game will work as such that using items such as Hides from creatures to craft a wearable item of clothing will provide you a certain amount of protection from a certain type of damage