To briefly cover a few bits..
Make it rain or throw water at the enemy and they'll get wet. This will decrease their resistance to cold/ice/lightning spells/attacks but increase their resistance to fire. A group of enemies in water? Lightning is your friend. Or turn it to ice and watch them slip and fall. Put some oil down and it will slow them down, or set it on fire. Create a steam cloud and you can move about unseen, or fire lightning into it and it becomes a static lightning cloud - not so good to be in. Set fire to poison clouds and they'll explode.
Loads of different weapons, with different stats and different speeds. Armours too. Make your own weapons, repair them or improve them. Make spells or skill books from scratch it you want, getting wood, making mush and then paper, getting feathers making quills... the list goes on and on.
Tactics, planning and a bit of luck count a lot in combat. It is fun, sometimes a scroll or potion in on of your packs makes all the difference. Don't hoard your goodies, use them..