Expresses the concept of 'even'; 'even in', 'even as', 'even to'.
Long explanation:
The 〜にすら grammar point is used to show surprise that an action or situation applies even to the noun in question. It can be translated into English as 'even in', 'even as', or 'even to'. It's usually used with negative sentences, emphasizing that 'even' in this particular case something can't or doesn't happen.