Advocatus diaboli

(def 2).
Historical Examples

I want to make certain—I’m advocatus diaboli,—I want your evidence that it was Beresford at all.
Sonia Married Stephen McKenna

No one since Lowe has taken up the part of advocatus diaboli against democracy which he played in 1866.
Studies in Contemporary Biography James Bryce, Viscount Bryce

My duty to my God I am discharging now, although to you I may rather appear as an advocatus diaboli.
The Strolling Saint Raphael Sabatini

When my conscience was noisy, the advocatus diaboli used to silence it by saying, “Oh, Strelitski’ll take it for granted.”
The Grandchildren of the Ghetto Israel Zangwill

You can never catch the advocatus diaboli asleep,’ concluded Raphael, laughing.
The Grandchildren of the Ghetto Israel Zangwill

Still, I must confess that, in advancing these arguments, I feel somewhat like an advocatus diaboli.
A Librarian’s Open Shelf Arthur E. Bostwick

Jimmy, advocatus diaboli in the matter, put the case for wrong-doing as strongly as he could.
The Smuggler’s Cave George A. Birmingham

Discussion of the eternal servant problem is apt to be one-sided; it was quite time that we heard from the advocatus diaboli.
Punch, or the London Charivari, Vol. 152, February 14, 1917 Various

The dramatist played the advocatus diaboli very cleverly, and the other side felt that its case had been stated fairly.
Our Stage and Its Critics “E.F.S.” of “The Westminster Gazette”

noun
another name for the devil’s advocate