Just putting out all ideas.
There could be:
-Spawnable mounts, or Eikthyr could be used as a mount after defeating it, or there could be a craftable saddle made to use Lox as a mount;
-Npcs with quests/npcs that show closest crypt/chamber/fuling village on map, or any other future structure;
-Npc that sells unique weapons;
-Dual wielding weapons;
-New weapon types, like spear that comes back to u after u throw it;
-Making items like feathers buyable from Haldor;
-Underwater world, or small islands all over ocean biome with new mobs on them;
-Unlocking flying at some point, being able to call Valkyrie to fly;
-Defeating bosses could unlock portals to different realm;
-God weapons/god powers/ god buffs, u could find shrines all over the world and interacting with them would give u some passive effect;
-Weapon enchantments, they would either add some mini ability instead of special attack or add like poison/fire/frost/spirit/lightning damage to weapon;
Basically game needs more options and different builds when it comes to gear.