So, Psychic phase, something close to my heart as I tend to run psychic heavy armies. Now there has been a massive change in the way psychic powers are manifested in 40k, no longer are we doing the ld test on 2d6 to get a power off, it is now following the route of Fantasy.
So basically it is all about how many psykers you have on the table, these contribute towards your Warp Charge pool.
Lets take a nice simple situation of a Mastery lvl 3 Librarian versus a Mastery level 2 Librarian.
Player A with the lvl 3 gets 3 dice then he rolls a d6 and adds that many dice to his Warp charge pool, Player B gets 2 dice from his lvl 2, and also adds the amount of dice from the result of the d6 player A rolled.
So lets say he rolled a 3, player A ends up with 6 dice, player B with 5 dice.
Take the perspective of Player A, these 6 dice are his Warp Charge pool. Assuming he rolled on Biomancy at the start of the game getting Iron Arm, Warp Speed and Endurance (he will also auto get Smite, more on this later).
So Iron Arm, Warp Speed, Smite are all warp charge 1 powers, Endurance is warp charge 2. So what you need to do in order to cast a psychic power is use your warp charge dice in order to meet the warp charge value on the power you want to use, so if I want to cast Iron arm I need to get 1 successful warp charge from my dice, how you get succesful warp charges is by rolling a 4+.
I want to cast Iron arm... it is plausible I would roll 3 dice to get at least 1 4+ to be able to cast it, if I want to cast Endurance being warp charge 2 I would need to get at least 2 4+ to make the power work.
The odds on these working is here......