Lord Chass had a "garden" where the "plants" were sculpted by nano-devices that built up vines and flowers out of steel and graphite in imitation of natural growth. When Gaunt first spoke to him he was in the garden pruning the steel roses with laser secateurs, and gave Gaunt a bloom that he pinned to his tunic. It gave just enough resistance to Asphodel's pistol shot to save Gaunt's life. The last scene of Necropolis is Gaunt scattering the ruined petals into the river as the ferry takes him away from the ruins of Vervunhive.