Which term describes a use of verbal irony with a biting or critical intent

Sarcasm

Explanation: Apex

I never got the secondary answer if there is one.

Sardonic: grimly mocking or cynical. Satirical: the use of irony, sarcasm, ridicule, or the like, in exposing, denouncing, or deriding vice, folly, etc. These are not exactly verbal irony, but language can definitely be satirical.

The Relative Clause is “who are five in number”. It is a type of dependant clause (it need the main clause in order to convey its meaning properly) that has the same function of an adjective; that is to say, it modifies a noun “friends”.