This is the 12135th most frequent Russian word.
икрой
The Russian word "икрой" means "with caviar" or "by caviar" (instrumental case of "икра," meaning "caviar").
In this sentence, "икрой" is an instrumental case noun denoting the accompaniment of the dish, specifically the caviar.
К нам на ужин принесли блины с икрой.
Pancakes with caviar were brought to our dinner.
Here, "икрой" is used figuratively in the instrumental case to describe an item that is exclusively consumed.
Он мечтает о жизни, где он питается только икрой.
He dreams of a life where he eats only caviar.
In this context, "икрой" refers to roe and is in the instrumental case, indicating the object achieved during the activity.