Weapon

Legendary Requires Attunement

Predators Instincts: You have Advantage on Initiative rolls.
Tlall's Claw: While you are holding Athame, it can function as a spellcasting Focus for your spells.

Thirsting Blade: You gain certain benefits when you acquire Devotion to Athame. When weilded by someone with no Athame Devotion, they suffer 1d8 Necrotic damage and 2 randomly determined minor detrimental properties.

Retaliation: When a creature picks up Athame without it's permission they must make a Charisma Saving Throw, taking (x) damage on a failed save or half as much on a successful save. The creature must repeat this saving throw at the start of every turn it continues to hold Athame

Devotion 10+.

Stalkers Grace: Whenever you use a Spell Slot to cast a Spell, you can immedietly teleport to an unoccupied space you can see within 15 feet of you.
Retaliation: DC 15, 2d6 Psychic
 

Devotion 25+

In for the Kill: While you are holding this focus, you can use it to cast Negative Energy Flood and Blur. Once a spell has been cast in this way, it cannot be cast again until the next dawn.
Retaliation: DC 18, 3d6 Psychic
 

Devotion 50+

Brutal Revelation: While attuned to Athame, you can cast Otherworldly Form from it. After you cast the spell, roll 1d6. On a roll of 1–5, you can't cast it again in this way until the next dawn.
Relatiation: DC 22, 5d6 Psychic