Verdant Core Deviant Classification
The Verdant Core deviation represents an abundance of vitality and plant life, likely caused by being implanted with supernatural seeds, contact with the Plane of Wood or the First World, or powerful primal rituals. Regardless of the source, you're a walking garden with grass, flowers, and other small plants sprouting from your flesh. You have powers over plants, wood, and growth.
Backlash
The flourishing plant life that covers your body is a part of you, but it draws nutrients from your blood, making you weaker the more the flowers grow. As the plants grow, you need to spend more and more time recuperating. Recuperating in the sunshine lowers this duration, as it feeds the flowers, speeding your recovery.
The same blood that lets one of the dragon-descended spit out a gout of flame is precisely what keeps the inside of their mouth from being singed in the furnace. Deviations, unfortunately, lack these safeguards, their powers coming from haphazard circumstance and interactions rather than intentional design. A character using their deviation always risks the chance of backlash.
Whenever you attempt to use a deviation, roll a DC 5 Flat. On a success, you use your deviation and the DC for subsequent checks increases by 5, to a maximum of 20 (DC 10 Flat DC 15 Flat DC 20 Flat); on a failure, you use your deviation and then suffer a backlash effect, after which your flat check DC resets to 5. Backlash progresses from mild, to moderate, to severe. When you have already taken mild backlash in a given day, the next time you would take backlash, you take the moderate backlash instead, and if you have already taken moderate backlash, you take the severe backlash instead, and your deviation can't be used for the rest of the day—attempting to use it simply brings pain. When you make your daily preparations, your flat check DC returns to 5 and your next backlash returns to mild.
Any effects from backlash can't be reduced, prevented, or otherwise bypassed. Conditions and damage you take from backlash can't be reduced or prevented by resistance or immunity, but still triggers any weakness you have to it.