The Salvation Seed was a genetically engineered plant that featured in the Hulk.
The Salvation Seed was a genetically engineered plant matrix created by the famous scientist Owen Candler who's research produced a flower that was perfect. However, due to extreme stress and his age; Candler died and collapsed on his creation. Despite crashing into the flower, the genetic matrix of the Salvation Seed bonded with the deceased scientist which recreated him.
The Salvation Seed is capable of bonding with a host body and regenerating it. Its quite capable of transforming flesh and blood into vegetable matter. The genetic nature of the seed allows it to be modified to create clones with memories of deceased individuals but are based on plant matter. These 'clones' were unable to realize their true origins and, at night, shaped back into their true form with roots digging into the ground to gain nutrients.
The creations of the Seed were capable of releasing a spore into the environment that had a calming affect on Humans. After bonding with a host, they were also capable of increasing the strength of a Human body.
One variant of the Salvation Seed grew into a massive flower with numerous tendril vines that were capable of ensnaring prey to devour. This flower was capable of spreading its seed and spores on a planetary level once it gathered enough energy. This plan was foiled by the Hulk and the Avengers.