Umbral Ally

You focus while whispering a short incantation. At the end of it, you put a piece of clothing on the mirror. It quickly sinks in and a moment later, an incorporeal humanoid or bestial creature draped in shadows is summoned from the inside. The second it appears, you estabilish a magical connection with it, similar to a mental link. The creature has 10 + 1d6 AC, 15 hit points and a flying speed of 45 feet, but it can’t attack. If it drops to 0 hit points or flies out of the range of your mental link (60 feet), the spell ends. You can make the creature invisible if you wish.

Outside of combat, the shadowy apparition can gently nestle around one creature (including the caster), granting that creature half cover. This effect persists one round after entering combat or when Umbral Ally moves away from the protected creature.

In combat, it acts directly after your turn. You can send it anywhere within the range of your mental link. While your Umbral Ally is within 5 feet of an enemy, you gain advantage on your attack rolls against that enemy. As an action, it can also create a shadowy barrier around you or one ally that you can see (and which is within 60 feet from you), granting him half cover that lasts until the end of the target's next turn. It cannot take any other action except for Hide, Disengage or Dodge. When you cast a spell with a range of Touch, your Umbral Ally can deliver the spell as if it had cast the spell. It must be within 60 feet of you, and it has to use its Reaction to deliver the spell when you cast it. If the spell requires an Attack roll, you use your Attack modifier for the roll. 

At Higher Levels: When you cast this spell using a spell slot of 2nd level or higher, the duration of the spell increases by 1 minute and hit points of the summoned creature increase by your character's level + 1 for each slot level above 1st.