Elysian Drop Troops
Elysian drop troops use tactics along the lines of using rapid deployment to throw troops straight into enemy lines. They are famed in battles such as the Taros campaign and the Anphelion project. Elysians come from Elysia, a planet about 30 light years away from Armageddon. Elysians are well trained in ship-to-ship boarding actions, and fighting in concert with orbital support when attacking enemies.
Training Elysians usually include throwing kids from the back of moving Valkyries until they learn to use grav chutes, or being shown how to clusterfuck even Orks from behind with only a lasgun. It is a good time to mention that the Guardsmen being trained to do these kinds of things all volunteered to do this, which adds some rather wiry hairs to their massive steel balls. If you are not a Cancer to Warhammer 40k (11 year old children) and actually use the correct tactics for the force, you'll find it invaluable to nonstop throw endless swarms of Valkyries filled with men at shootie armies such as Tau. But such a fast army comes lightly armoured and fielding Leman Russ Battle Tank or even Chimera is impossible if you want to keep up.
The Valkyrie heavy deployment tactics employ a lot of scouting, deep striking and infiltration, but, this is not as effective as infiltrating a squad of Leman Russ executioners with a little... Tactical Genius.