2 questions about this ability. First, it states it's action type is passive. Does this mean you could choose to not maintain it and just cast it whenever you are hit or does it mean it is a passive action to use your shield once you are already maintaining it? Second, I understand that these shields bleed off 5lp per turn until they reach the state that your natural potential can maintain. It isn't clear on the secondary aspect to this shield when cast at high level though. What happens to the damage barrier and blocks energy aspect of the shield when it is cast at a level of 280 but can only be maintained at 180?

I'm glad you asked. These answers are pretty straightforward.

A passive action (regardless of whether or not it's a psychic power) can be used at any time. Defenses are typically passive actions, along with some other actions listed on page 79 of the English Core. The key for Psychic Powers on page 195 states "Action: Indicates whether the use of the Power is an Active or Passive action." Note that "use" in Anima refers to the activation of a power, because maintaining a power does not change its activation requirements (if it did, Psychics would be even MORE OPP). So, yes, you can utilize the power whenever you're hit if you don't maintain it, but doing so means you run the risk of fumbles, and any modifiers that might not have been there last time. A maintained shield might always be at its lowest activation potential, but at least it's constant, neh?

The second one is answered simply enough by the following passage on 194 of the English Core. In an example for maintaining psychic powers "Pazusu’s psychic potential is +80, which allows him to Maintain his Innate Powers at a Medium Difficulty. If he successfully employs a Psychic Shield and allows it to remain active in subsequent turns, it will have a Medium effect regardless of what his original Final Potential Calculation was." The important words here are "Medium effect," which implies that it's not just the LP, but all effects of the power being reduced to what they would have at the medium level. Now, since there are no exact rules for when the additional effects disappear during degradation, your GM can play it one of two ways:

1. The extra effects disappear immediately, though the LP drop goes at its normal rate.

2. When the LP drop (through attacks as well as degradation) would bring it down below an effect level that has those bonus effects, the bonus effects are lost.

Edit: Also, call it a memory blank, but I honestly can't recall where the rules for the shield bleed are located. A rapid search through the Core, Core Exxet, The GM's Toolkit, Dominus, and Arcana didn't bring up a result (though, I'll admit, this was a very rapid search), but I do remember hearing about it somewhere. I just can't recall where and wanted to have it for reference. If anyone else remembers, please let me know, because otherwise I may have to start going with what the example I quoted actually says (an immediate drop to the Innate Potential).

Nevermind, found it. It's only listed under every shield ever , Tyr. Gosh. Psychics OPP.

Anyways, I hope this helps.