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Was browsing over the Apocalyptic History-section of GW, found a somewhat larger version of the picture used on the cover of the Macragge rules book, and noticed the bio-titans in the background. Anybody have any theories what they might be?
They clearly aren't Hierophants of the current design, bearing more similarity to the old-design Hierophants with Ripper Tentacles, but they'd lack the bioweapon arms those have. Haruspex, Exocrine, Malefactor and Dactylis can also be counted out at least based on the old designs, and Exocrine and Dactylis would also be ruled out due to established battlefield roles.
I'd really like for GW to expand a bit on the various Tyranids, but then they'd of course be bugged about rules and models for those. ^_^; Of course, not the first time we're teased with a view of something monstrous that isn't in the game... The Tyranid Artwork section has many pictures dating back to 3rdEd with shadowy, monstrous things in the background.
And in case people want to see what old Epic Tyranids looked like, here's a nice page I found: Epic Tyranid Gallery
"The meat things seek to destroy ourselves. They hunt us as we hunt them but they are weak and uncertain. The inferior flesh will be entirely destroyed, all biomatter consumed. Ourselves will fight to the last, all weak flesh must be devoured."
Those critters lurking in the background could be all kinds of things. Tyranids are a constantly evolving race with lots of new creatures being cooked up all the time. The things you are looking at could be variants on the more commonly seen Bio-titans.
I know that in the picture that was used as the cover of the previous Tyranid codex that huge thing in the background is a Dominatrix. There are other things lurking about in other pictures but some of these are just Hive tyrants and Carnifexes.
I think that the giant insecty thing in the picture you showed there is probably a variant on a Hierodule. It looks roughly the same size but more light weight and possibly faster. You must also consider that the people drawing these picture are using artistic licence.
They are just drawing giant thing which could be who knows what. There is also the fact that many Tyranids have changed over the years a great deal. If a Malefactor or Haruspex were to be released both of them would differ a great deal from the original epic versions.
Basically those things in the background are often something which the artist made up while they were working, because Tyranids change alot there is no need for them to be specific about what it is.