Pact of the Watcher

From beyond the Prime Material Plane your patron watches over fates of mortals. They might guard the veils between life and death, control luck or be the harbinger of an apocolypse. These beings can be inscrutable, considering life and death, weal and woe nothing more than part of the balance or fundamental workings of the universe. Depending on your patron, they might see that balance as something they must protect or something that is theirs to alter on a whim.
Your patron might be the Raven Queen, the Norns, the Morrigan, an Oracle, the Grim Reaper or some other manifestation of Fate.

Fate Determined

Your patron grants you a better understanding of the way fate unfolds. You learn the Guidance cantrip.

Sentinel Familiar

Starting at 1st level, you gain the service of a spirit sent by your Patron to watch over you. The spirit assumes the form and game statistics of a tiny beast from the option list of the Find Familiar spell, except you can add your Proficiency Bonus to their natural AC and their hit points are calculated by your Proficiency Bonus + 2 times your Warlock level. You choose the Pact Familiar type as celestial, fey, or fiend instead of a tiny beast.

While your familiar is perched on you or being carried by you, you gain darkvision with a range of 60 feet (or increase your existing darkvision by 30 feet). You also get a bonus to your Wisdom (Insight) and Wisdom (Perception) checks equal to your Charisma modifier.

While perched on you or being carried by you, your familiar can't be targeted by any attack or other harmful effect; only you can cast spells on it; it can't take damage and it is incapacitated.

If it is slain by a creature, you gain advantage on all attack rolls against the killer for the next 24 hours. The familiar doesn't require sleep. While it is within 100 feet of you, it can awaken you from sleep as a bonus action.

The Pact Familiar vanishes when it dies, if you die, or if the two of you are separated by more than a mile without being telepathically connected. At the end of a short or long rest, you can call the Pact Familiar back to you —no matter where it is or whether it died— and it will reappear within 5 feet of you. You cannot change its form when you resummon it.

Fate of All

At 6th level, your link to your patron allows your touch to grant your enemies a glimpse of the grave, the ultimate fate for all mortals. When you cast a spell that deals cold or necrotic damage, you can empower the spell with a touch of the void beyond life. A spell empowered in this way ignores resistance to cold and necrotic damage, and creatures with immunity to cold or necrotic damage take half damage instead.

Additionally, choose one of the following effects:

- You regain hit points equal to half the necrotic damage taken by one target of the spell.
- One creature who took cold damage from the spell has its movement speed halved for a number of rounds equal to the level of the spell (minimum 1). A creature immune to cold instead has its movement speed reduced by 10 feet for the same duration.

You can use this feature a number of times equal to your spellcasting ability modifier (minimum once), and you regain all expended uses when you finish a long rest.

Sentinel Soul

Also at 6th level, you gain the ability to merge with your familiar.
As a bonus action when touching your familiar, your body merges with its form.
While merged, you become Tiny, you replace your speed and hit points with your familiar’s. You cannot use the Attack action while in this form.
If you drop to 0 hit points in this form you return to normal and your familiar dies.
As another bonus action, you can return yourself and your familiar to normal.

Sentinel Shield

At 10th level your familiar has developed enough of a bond with you that it will act to save your life. When you would take damage from any source you can use your reaction to have your familiar take that damage instead. If you do so you cannot resummon your familiar for 1d4 days.

Scales of Fate

At 14th level you can cast the spells Harm and Heal. If you cast either of these spells you cannot use this feature again until you finish a long rest.