sentinel
noun
a person or thing that watches or stands as if watching.
Used to describe actions that started in the past and continue into or have direct relevance to the present.
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
"I come," she said, "to save your life, which is else in great peril—if you answer me, speak as low as you can, for they have sentinelled your door with armed men."
From The Monastery by Sir Walter Scott