Bind Myrmidon

You trace magical runes across the armour and weapon to summon forth an elemental spirit and bind it to your service. At the end of the casting an Elemental Myrmidon rises and remains under your command until it dies or you die. The myrmidon's element depends on the material used during the casting of the spell. 

When the spell ends the spirit returns to it's home plane.

In combat the myrmidon rolls it's own initiative and is under the DM'S control but acts to defend you. On your turn you can order the myrmidon to move (no action required) and can use a bonus action to order it to attack, dodge or disengage. You can order the myrmidon to stay in one location or to travel with you.