What is the language technique used in phrase cold within him froze his old features?

The language technique used in the phrase "cold within him froze his old features" is personification.

Here's why:

* Personification: Giving human qualities or characteristics to inanimate objects or abstract concepts.

* In this case, "cold" is an abstract concept (a feeling or state), and it's being attributed the ability to "freeze" physical features, which is a human action.

This technique creates a vivid image and emphasizes the coldness and detachment of the character. It suggests that the character's internal coldness has a tangible effect on their physical appearance, making them seem older and less vibrant.