Here is more information on these powers
Originally by Katie Drake via AgeOfEgos
The power mentioned is (I think) the new Holocaust. How I was told that it works is as follows:
Lets say we have a unit of 20 Gaunts charging some Grey Knights. One of the Knights has the Holocaust power. After assault moves are done but before attacks are resolved, the Grey Knight passes his psychic test to use Holocaust. Each model in the enemy unit is hit once by an attack that always wounds on a 4+ and allows normal armor saves.
What that basically means is that before anyone gets to swing, the Knights can blow through half of a unit that has a poor armor save. In the above example, we're looking at 9 dead Gaunts most likely - and that's before the Knights attack.
I've heard stuff about Hammerhand. Basically, it's cast in the assault phase, and the casting unit gains +1S until the end of the turn which is awfully nice when everyone's packing a force weapon.