Arm of the Old Ones

Reach your arm to the heavens and request strength from your patron, receiving their a fraction of their power and consuming one 7th level spell slot.

A spiritual, translucent arm will cover the arm risen to the sky, granting double melee range and 4d8 force damage to an unarmed strike. However, you are unable to cast offensive spells and use other melee weapons until the arm is dismissed or a long rest is initiated. 

If cast at 8th level, you may slam your great fist onto the ground, dealing 2d8 radiant damage within a 4m area, requiring a DC 15 DEX save to not fall prone. This consumes an action.

If cast at 9th level, 2d8 attack dice is added to both abilities.