Avatar of the Grimreaper

Incorporeal Movement 
The avatar can move through other creatures and objects as if they were difficult terrain. It takes 5 [rollable (1d10 {"diceNotation":"1d10","rollType":"damage","rollAction":"Incorporeal Movement","rollDamageType":"force"}[/rollable] force damage if it ends its turn inside an object.

Turning Immunity 
The avatar is immune to features that turn undead.

Come and see, his name is...
 If damage reduces Avatar of the Grimreapers to 0 hit points, Avatar of the Grimreaper instead drops to 1 hit point unless the very existence is destroyed.

Shadow of Creation.
Only the summond creatur can see the Avatar of the Grimreaper

Uneasy Omens 
Once the Grimreaper chooses its target all lights flicker (lanterns, torches, etc.).

The last you see
The Grimreaper is invisible to all but the character the Grimreaper is targeting.

Grimreapers Touch
The attack of the Grimreaper ignore all resistances and immunities and the damage Reaping Scythe deals counts as if the creatur has Vulnerability to all damage typs.

Reaping Scythe
The avatar sweeps its spectral scythe through a creature within 5 feet of it, dealing  (1d12 + 10) * charakter level damage slashing damage plus (1d12) necrotic damage.

From Death there is no Escape 
When ever the Grimreaper's target ever: uses there movement, disengages, dashes or moves what so ever the Grimreaper can teleport the direction the target was heading. the Grimreaper instantly succeeds perception checks to find a hiding target.

Also the Grimreaper can teleport instandly behind its target when it is bannisched from the current plain of existance.