Your pact draws on power from an undead warrior of days long past. When you choose this subclass, you might make a deal with an ancient ruler, skilled in personal combat, but given over to the realm of the unliving.  Your patron provides martial prowess, tainted by the silent powers of the undead.

The Arms of Old

Your patron's knowledge of battlefield defense give you proficiency in medium armor and shields.  Additionally you are infused with the martial prowess to utilize the weapon mastery of one weapon for which you have proficiency.  You may change your weapon mastery after each long rest.

Ancient Warleader Spells

The magic of your patron ensures you always have certain spells ready; when you reach a Warlock level specified in the Ancient Warleader Spells table, you thereafter always have the listed spells prepared.

Ancient Warleader Spells

Warlock Level	Spells
3	Shield, Command, Heroism, False Life
5	Fear, Vampiric Touch
7	Blight, Compulsion
9	Contagion, Legend Lore

Imbued Training

Your patron imbues you with the power to attack twice, instead of once, whenever you take the Attack action on your turn.  Moreover, you can cast one of your Warlock cantrips that has a casting time of an action in place of one of those attacks.

Resilience

Your patron teaches you to turn aside blows.  You have resistance to slashing, piercing, and bludgeoning to non-magical attacks.

Fear of the Dead

When you critically hit a creature, you can use a bonus action to have your patron exude a feeling of dread through you.  All enemies within 60 feet must succeed on a Charisma saving throw against your spell save DC, or they are frightened. The target struck takes 8d10 Necrotic damage if it can be frightened.

Once you use this feature, you can’t use it again until you finish a Long Rest unless you expend a Pact Magic spell slot (no action required) to restore your use of it.