This must be the Legion 5-pack that was mentioned at the UK Toyfair.

Note that it is "existing tooling with new character decos", and we already know two of the toys are being released in the main line (Twinstrike & Hun-gurr)... so we should see all five released at stores individually for us to build Abominus, but the 5-pack will allow people to get the whole set easily. (with some different decos)