Wrath creates an explosion of purple flames from the user's body during LoToN
Gluttony allows the user to absorb chakra streamed into the ground for three turns during LoToN
Rebirth allows you to absorb your own energy-based attack and send back a replica composed of dark release. An interesting twist is that it's released in the same state of matter e.g. rather than purple flames, it will be violet lightning if a raiton technique was absorbed.
Yeah, this last one might be the coolest of the four. After absorbing three A-Rank techniques (oddly specific trigger), the user can coat themselves in an armour of dark chakra that has three purposes. Offensive allows you to create weapons from the armour, defensive allows you to absorb techniques into the coating, supplementary lets you absorb chakra from the opponent's body or boost the damage of your Dark Release techniques. This jutsu also enables the release of any S-Rank or below Genjutsu upon being activated. All in, pretty awesome technique.