Great Old Grasp

Once per long rest you can use this feature to restrain a creature you have hexed. This counts as a bonus action. 

Tendrils swarm around the hexed creature as your patron ensnares the target in his tight grasp. The creature must succeed on a dexterity saving throw equal to your spell save DC. On a failed save the creature is restrained. A creature restrained can attempt to break out at the end of each of its turns, though the DC increases after each failed save by 1. 

This feature can be used twice at 10th level and 3 times at 17th level.