I was pondering about how parasitic Watch Tower was and looked it up on wiki:
https://en.wikipedia.org/wiki/Parasitism
Interestingly, Watch Tower is not parasitic, as a parasite does not destroy its host - the host sustains the parasite.
Instead Watch Tower is a parasitoid, which "unlike a true parasite, however, it ultimately sterilizes or kills, and sometimes consumes, the host."
Very apt description.