Here are new options for warlocks when they choose a new eldritch invocation.
Prerequisite: eldritch blast cantrip
You channel primal destructive forces through your eldritch blast. When you cast that cantrip, you can choose to deal acid, cold or fire damage instead of force damage.
Magical difficult terrain does not impede your movement and you have advantage on saving throws made against spells that restrain you.
Prerequisite: 7th level, the Reaper patron, Pact of the Tome
You steal magical energy from a recently deceased creature. When a creature you can see within 60 feet of you dies, you can use your reaction to regain an expended warlock spell slot. The dead creature's true name is etched into a page of your spell tome.
Once you use this feature, you can't use it again until you finish a long rest.
Prerequisite: find familiar spell
Your familiar has +10 to Stealth checks and can't be tracked except by magical means.
NO MERCY FOR THE DYING
Prerequisite: 5th level, the Reaper patron, eldritch blast cantrip
You can cast eldritch blast as a bonus action if you only target creatures with 0 hit points with your attacks.
Prerequisite: 5th level, the Bringer of the Apocalypse patron, eldritch blast cantrip
You unleash a storm of apocalyptic lightning. When you hit a creature with eldritch blast, you can cast lighting bolt as a bonus action using a warlock spell slot. The spell must travel through a creature you hit with eldritch blast.
SCYTHE OF SEVERING
Prerequisite: 12th level, the Reaper patron, Pact of the Blade feature
When you drop a creature to 0 hit points with an attack from your pact weapon, the creature dies without making any death saving throws. The creature cannot be resurrected unless the resurrection is done by a god, demon lord, or archdevil.
SHELTER FROM THE STORM
Prerequisite: 15th level
You can cast fire shield at will, without expending a spell slot or material components.