Lifeblood is a major update to Hollow Knight originally planned for the release of the game on Nintendo Switch. It was pushed to beta testing on March 23rd, 2018, with its name and content revealed on the 24th. Lifeblood was then released on April 20th, 2018.
This last content pack tweaked the game mechanically, added new soundtrack and included a new boss, shown in the media gallery.
This content pack is very subtle, some people can't notice the difference, but for people knowledgeable about the bugs of the game it was a great deal.
The Lifeblood DLC introduces the following features