Eldritch Strike

Eldritch energy envelops your fists to allow you to deliver an arcane strike within melee range. Make a melee spell attack against the target. On a hit, the target takes 1d8 force damage, and is pushed backwards 5 ft in the opposite direction.  If the warlock has the Agonizing Blast invocation, they can then add their spellcasting damage modifier to each damage roll.

The spell allows for an extra strike when you reach the levels of 5th level (2 strikes), 11th level (3 strikes), and 17th level (4 strikes).