The new dataslate Tyranid Invasion: Rising Leviathan II is now available in both ebook and interactive ipad. This gives us a total of 10 formations for Tyranids, and really helps break the no allies rules for Tyranids, with a lot of flexibility for creating lists for the tabletop.
While I have not read through the entire background of Rising Leviathan II, what I have read I enjoyed and am reserving for a good time to sit down and enjoy it. On the interactive version, there are about 10 pages of background and story on the how the Tyranid Swarm Leviathan invaded the planet Satys.
As for the formations here is what you have in store for you. Note there are some additional restrictions not listed here.
1 Tervigon and 3 termagant broods and gain the Hyper-Progenitive special rule. This allows you to re-roll ones when spawning termagants. This will help get more out of your spawns.
1 Tyranid Prime and 3 Warrior Broods which gives all models a synapse range of 18" in this formation. Definitely some use here in spreading Synapse across the board.
1 Hive Tyrant, 1 Hive Crone, 2 Harpies, and 3 gargoyle broods. They come with Objective secured which allows gargoyle units in the formation to control objectives even if enemy scoring units are in range. Just as well, the formation comes with Skyswarm which allows any destroyed gargoyle units in the formation to immediately be replaced by an identical unit (including upgrades) in ongoing reserves.
1 Excocrine, 3 Biovores, 1 Tyranid Warrior Brood and comes with Organic Bombardment which gives all ranged weapons pinning and the ability to re-roll scatter dice on blast and barrage weapons.
3 Hormagaunts Broods, 3 Termagant Broods, 1 Warrior Brood and come with Endless Swarm. This allows identical units a 4+ chance of coming back into ongoing reserves.
Overall I like these formations, and I am sure some will find their ways into tyranid lists. In fact I wouldn't be surprised if a couple of these combined made were added to lists.
Beyond the formations, there are several pages of Tyranid Showcases and two Echoes of War missions. Overall I like the book, but since I am not a Tyranid player I will leave the critique's to those that are. I really hope that we see more of these for Tyranids as time goes on past Rising Leviathan III, which is due next for Tyranids.