Does cinnabar react with iodine?
I did a cursory search and found some information particularly from books of late 19th century(1,2):
Cinnabar and iodine

On heating, it (cinnabar) is readily decomposed with formation of small scarlet crystals of mercuric iodide.

Cinnabar and bromine

[...] After digesting the cinnabar with excess of bromine liquid (or bromine water containing 3% of bromine or solution of hydrochloric acid containing 13% of bromine) for a few days, the whole is dissolved, and also any metallic mercury present [...] The amount of bromine required is very considerable, 1 part of mercury is obtained and 3.5 parts of hydrobromic acid remains in the solution.

References

Chemical News and Journal of Industrial Science, Volumes 37-38, Chemical news office., 1878
Dictionary of Arts, Manufactures and Mines by Robert Hunt, Andrew Ure, 1878