The Circle of Twilight seeks to exterminate undead creatures and preserve the natural cycle of life and death that rules over the cosmos. Their magic allows them to manipulate the boundary between life and death, sending their foes to their final rest while keeping their allies from that fate.

These druids seek out lands that have been tainted by undeath. Such places are grim and foreboding. Once vibrant forests become gloomy, haunted places devoid of animals and filled with plants dying a slow, lingering death. The Circle of Twilight goes to such places to banish undeath and restore life.

Source: Unearthed Arcana 23 - Druid

Harvest's Scythe

Starting at 2nd level, you learn to unravel and harvest the life energy of other creatures. You can augment your spells to drain the life force from creatures. You have a pool of energy represented by a number of d10s equal to your druid level.

When you roll damage for a spell, you can increase that damage by spending dice from the pool. You can spend a number of dice equal to half your druid level or less. Roll the spent dice and add them to the damage as necrotic damage. If you kill one or more hostile creatures with a spell augmented in this way, you or an ally of your choice that you can see within 30 feet of you regains 2 hit points per die spent to increase the spell’s damage, or 5 hit points per die if at least one of the slain creatures was undead.

You regain the expended dice when you finish a long rest.

Speech Beyond the Grave

At 6th level, you gain the ability to reach beyond death’s veil in search of knowledge. Using this feature, you can cast Speak with Dead without material components, and you understand what the target of this casting says. It can understand your questions, even if you don’t share a language or it is not intelligent enough to speak.

Once you use this feature, you can’t use it again until you finish a short or long rest.

Watcher at the Threshold

At 10th level, you gain resistance to necrotic and radiant damage. In addition, while you aren’t incapacitated, any ally within 30 feet of you has advantage on death saving throws.

Paths of the Dead

At 14th level, your mastery of death allows you to tread the paths used by ghosts and other spirits. Using this feature, you can cast Etherealness. Once the spell ends, you can’t cast it with this feature again until you finish a short or long rest.