Dungeons & Dragons is testing out a Warlock patron that will give Warlocks the ability to explode when they die. Earlier today, Dungeons & Dragons released two new subclasses for public playtesting, presumably for inclusion in an upcoming product. The new subclasses include a "College of Spirits" Bard that communes with the dead to hear their stories, and an Undead patron for Warlocks that gives them powerful abilities to separate their soul from their body. Notably, the Undead patron gives Warlocks the ability to explode when they reach 0 Hit Points, dealing damage to all around them and causing their body to instantly re-form with 1 HP.
In less explosive content, the College of Spirits provides players with the option to create a Bard who speaks with the dead using "gaming sets" such as a Tarokka Deck and a talking board. College of Spirit Bards' most powerful ability is the ability to store one of 12 "tales" from beyond, chosen randomly from a table by rolling a Bardic inspiration dice. These tales can either be used as friendly buffs or as powerful tools to deal out various kinds of damage and effects in battle. These bards can also temporarily learn divination and necromancy spells from any spell class, provided they complete an hour-long seance.
The Undead Warlock provides all sorts of fantastic thematic abilities, including Warlocks gaining a "Form of Dread" that provides temporary hit points, provide immunity to being Frightened, and gives them the ability to cause a hostile creature that attacks you to become Frightened. By the time they reach Level 10, the Undead Warlock gains resistance to necrotic damage and gains their explosive death ability. At Level 14, players can separate their body from their spirit and cause players to regain hit points whenever they deal out necrotic damage.
While it's certainly possible that these new subclasses are related to the Planar subclasses, we will note that both of these subclass seem to have thematic ties to Ravenloft, the gothic horror-themed campaign setting explored in Curse of Strahd. With Curse of Strahd getting multiple new editions this fall, could it be possible that a new Ravenloft-related book is on the way? You can check out the new subclasses on D&D's webpage.