Battle Infusionist

You are able to enhance your weapons to change the damage type to your advantage. Infuse your sword with fire magic to combat an army of twig blights, your arrows with divine power to still the undead marching on a city, your way is block by a wall and all you have is a dagger; infuse and change the piercing to bludgeoning and break your way free.

Perhaps battling your way out is not an option and you need to shield villagers as they escape. Infuse your armour with thunder magic to resist the onslaught from a lighting mage hurling lighting bolts, your shield with slashing resistance as a mutated pirate with four arms swings his scimitar's.

Whether an army stands in their way, or hidden in the shadows an infusionist knows how best to use their magic, either the devastating blow or the unstoppable shield. 

Proficiency Arcana

Starting level 3 you gain proficiency in Arcana if you do not already have so.

Infusion magic

Starting at level 3 you can infuse magic into your weapon, shield or armour granting it magically properties. As a bonus action you can magically change your weapons damage type to something else: swap to piercing, slashing, bludgeoning or elemental fire, ice, lighting etc even necrotic, divine, poison whatever the infusionist believes will best their enemies. Alternatively you can infuse magic into your shield or armour to gain resistance to the damage type. You have 3 infusion slots and gain 1 with every level in fighter, each slot last for one round until the start of your next turn, multiple slots may be used in one bonus action on only one item of equipment. Slots are recovered after a short rest.

Knowledge of weakness

Starting level 7 you gain insight into your enemies weaknesses. Using a bonus action you can spend one infusion slot to learn one, if any, vulnerability of an enemy that you can see.

Mass infusion

Starting at level 10 you have learnt to infuse multiple items at once. You can now use one infusion slot to infuse magic into both weapon and armour/shield to gain resistance as well as exploiting an enemy's weakness.

Superior knowledge

Starting at level 15 your trained eyes can determine multiple creatures weaknesses. Using a bonus action to spend one slot you can target multiple different enemies that you can see and gain insight into all of their vulnerabilities.

Infusionist

Starting at level 18 your infusion magic can extend to any item. As a bonus action you can infuse magic into any item to give it resistances or damaging properties, including an allies weapons and armour at a range of 5ft.