Imagine
Imagine was a roleplaying magazine published by TSR UK between April 1983 and September 1985. It ran for 30 normal monthly issues plus one special issue. Generally the magazine focused on D&D and AD&D, but it sometime featured other games systems too, especially in special issues.
Here is a list of the significant references to Cthulhu-related things in Imagine. Very short passing references to new publications are not included here, but rather more substantive things like scenarios, articles, lengthy reviews, and really obscure things worth noting like references to small-print fanzines with Cthulhu content.
Note that issue 13 was a "special edition celebrating the work of the Master of Gothic horror H.P. Lovecraft".
Also note the capitalisation of fanzine titles, sometimes in all caps, is reproduced below as printed in the magazine.
No 8, Nov 1983, p39, under Fanzines, notes Tempestuous Orifice 3 had articles on subjects including Call of Cthulhu
No 13, Apr 1984, pp2-4, "Put a little terror into your life: a cautious peep at the Call of Cthulhu game" by Steve Norledge
No 13, Apr 1984, pp7-9, "The Mirror of Nitocris" short story by Brian Lumley
No 13, Apr 1984, p11, "Howard Phillips Lovecraft (1890-1937)" by Paul Cockburn
No 13, Apr 1984, pp15-18, "Darklaw: a Call of Cthulhu Mini-scenario" by Simon Redgrave
No 14, May 1984, p32, under Fanzines, notes Tempestuous Orifice 4 has Call of Cthulhu scenario
No 15, Jun 1984, p4, IMAGINE magazine GAMESFAIR POLL, Call of Cthulhu voted Best RPG in any other category (not fantasy or sci fi)
No 15, Jun 1984, p19, lengthy review of The Cthulhu Companion
No 15, Jun 1984, p36, several letters praising Imagine Cthulhu special issue 13
No 16, Jul 1984, p46, more praise in letters for Cthulhu special issue 13
No 17, Aug 1984, p49, letter from Peter Jeffrey correcting impression of Lovecraft given in issue 13 article and issue 15 letter
No 20, Nov 1984, p53, prominent advert for fanzine Tempestuous Orifice 4 saying it features a Call of Cthulhu scenario by Imagine's Simon Redgrave
No 21, Dec 1984, pp20-21, lengthy reviews of Call of Cthulhu scenarios Death in Dunwich, The Arkham Evil, Curse of the Chthonians, and The Fungi from Yuggoth
No 21, Dec 1984, p57, brief review of DAGON 3 Call of Cthulhu fanzine
No 22, Jan 1984, p52, review of DAGON 4 Call of Cthulhu fanzine
No 23, Feb 1984, p40, reviews fanzine STARQUESTER which covers many games including Call of Cthulhu
No 24, Mar 1985, p48, readers survey includes praise for Call of Cthulhu issue: "Our most successful foray into other systems seems to have been with issue 13; 'although I don't play Call of Cthulhu, I found this very interesting' (Simon Curtis)"
No 24, Mar 1985, p52, review of fanzine MANIC DEPRESSIVE which includes "a useful checklist of ancient tomes for CoC"; review of fanzine PROTOPLASM which has "a very short Cthulhu page"; review of fanzine DEAD ELF 2 which has "a fairly large and well-written Call of Cthulhu scenario"; review of DAGON 5
No 25, Apr 1985, pp52-54, review of RUNESTONE 5 fanzine which includes Call of Cthulhu scenario; review of THE FIERY CROSS 3 fanzine which also includes Call of Cthulhu material (seems to be "The Mystery of Greenfields" scenario)
No 26, May 1985, p39, brief report of Games Workshop encouraging Cthulhu adventure writers, like Marcus Rowland and Pete Tamlyn
No 26, May 1985, p53, brief review of PROTOPLASM 2 fanzine with Call of Cthulhu scenario; review of DAGON issue 6
No 27, Jun 1985, p53, review of new zine ZADRAGORZETTE which was considering running and featuring a Call of Cthulhu game in future issues
No 28, Jul 1985, pp20-23, "A look at the Cthulhu Mythos" by David Hill
No 28, Jul 1985, pp25-32, "A Nice Night For Screaming" scenario by Marcus Rowland compatible with Call of Cthulhu
No 28, Jul 1985, pp52-53, review of DEAD ELF 4 fanzine which includes a detailed Call of Cthulhu scenario
No 29, Aug 1985, p50, review of STARQUESTER 2 fanzine which has material on Cthulhu in 1985 "including a new Zine Editor class"; review of CHAOS LORD fanzine which includes "a rather powerful addition for Call of Cthulhu called Cthulhu Busters"
No 30, Sep 1985, p50, review of new postal game zine DANSE MACABRE which offers various games for play including Call of the Cultists, a Cthulhu-based card game, and a major postal RPG game detailed in 24-page supplement to the zine based on Call of Cthulhu "in a future where Cthulhu's minions have invaded and successfully conquered the Earth"
