Looking at Nessie result in

UNDEFINED

please update line 2207 of AvventuraNelCastelloJS.js

description: i18n.AvventuraNelCastelloJS.rooms.rock.interactors.nessie.description,

instead of

description: i18n.AvventuraNelCastelloJS.rooms.rock.description

I apologize

If you're still using the older 1.0 version of the game, line 2224, "scoglio: -> interactors: -> mostro:" update the description tag as above