The Reaper

Necromancy is typically a frowned upon practice. Thankfully, most necromancers don't spend most of their time around living creatures. Though scarce, warlocks who follow the path of The Reaper make use of the core skill of soul snatching, commonly referred to as "Hijacking," in which they forcefully seize the soul of a recently deceased individual and force that soul back into it's body, rendering them a puppet of the warlocks whims, though only temporarily. Though warlocks are already typically shunned, Reaper Warlocks are looked down upon by most all other pious groups, especially Clerics and Paladins. The only creatures capable of creating this type of pact with a mortal are the three celestial reapers: Onir, Ulphin, and Cilan. They are neutral beings, only seeking to ensure the things that must die end up dead. What occurs with reaped souls is not their concern, and as such they do not care for what their warlocks do with the power granted to them. The only thing that matters is the creation of souls. 

Reaper's Boon

The Gifts every fledgling necromancer is granted, and the very basic abilities available to you.

Soul Anchor: Starting at 1st level, when a hostile humanoid creature of medium or smaller size (and CR of <1) is slain you may take a bonus action to wrap their soul in ethereal chains and anchor them to their body. This anchor lasts for one hour, or until dismissed as an action. While the soul is anchored, you may take a bonus action on your turn to have it either move, attack, or otherwise perform an action it is capable of performing. Only one soul can be anchored at a time, and once the anchor is ended the soul is freed. Attempting to anchor a new soul will result in the previous being freed. 

Soulsight: Starting at 1st level, you are able to perceive mortal souls within 30 feet of you. This includes souls which have yet to die or are still within bodies. This ability does not work through any sort of cover or magical effects, such as the Darkness spell. 

Eternal Servants: Starting at 1st level, you are able to trap up to two medium sized humanoid or smaller souls (and CR of <.5) within your catalyst. As a bonus action, you can summon these souls to the mortal realm and anchor them to yourself as your personal servants. During your turn, you may take a bonus action to have the souls either move, attack, or otherwise perform an action they would be able to perform. If the souls are not slain they may be returned to the catalyst as a bonus action. If the souls are slain or otherwise escape, they must be replaced with souls in the battlefield or are refilled during a short/long rest. Upon taking this pact the Warlock is granted two of these souls. 

Upon reaching more than 60 feet from you, anchored souls or summoned souls will be freed from their chains and must either be recaptured or they will escape.

Soul Siphon

Starting at 6th level, you may make an action to absorb one of the souls stored within your catalyst to regain up to 3d6+4 hp. Additionally your capacity for stored souls is increased to 4 and to a maximum combat rating of 1 1/2.

Your capacity for anchored souls is increased to 2 and to a maximum CR of 3.

Great Soul Prison

Starting at 10th level, your capabilities as a necromancer have vastly improved. You are now able to hold up to 6 spirits within your catalyst or anchor up to 3 medium size (CR <4) humanoid spirits OR one large humanoid (CR<8) or one large creature (CR<8). 

Lord of the Undying

Master Necromancy: Starting at 14th level, you are now a master necromancer. You are able to utilize your soul siphon ability up to 2 times per turn, and your capacity for souls within your catalyst have increased to 10 (Medium size, CR<5). You are now able to contain up to one large humanoid (CR<10) within your catalyst instead of the 10 small creatures. As a master necromancer, you are able to anchor up to 5 medium size souls (CR<10) at a time/two large souls (CR<15)/or one Huge soul (CR<20) for up to two hours or until dismissed as an action. 

Draining Touch: Starting at 14th level, as an action you are able to touch a creature and drain their life points up to 5d6+5 and add them to your own, either as life points or temporary life points.