Need a usefull war pve build for chimeric prism

You can run whatever you want with it. Using it instead of a regular shield means you lose out on health and some form of damage mitigation, which obviously makes you easier to kill but doesn't have any functional impact on how your build operates. If the only reason you want to use the prism is for something like aesthetics or roleplay, then you can just use it along with your standard sws/dslash/hundred blades/whatever builds. It's use doesn't make any changes mandatory.

If you were looking to somehow leverage the +5e to justify it's use then that's a lot harder. Boosting your maximum energy does not constitute energy management. If you want the latter, you'd use a zealous weapon and/or a skill such as Auspicious Blow. Raising your maximum energy is typically only useful in situations where your build involves unloading most/all of it at once, which is not something you'd typically do, and even if you did I suspect you'd be better off doing that with a +5e weapon before swapping back to a 15^50.

So, if you want to stay on the Chimeric Prism to look at it while you play, it means you want to leverage the +5e so it has a point.

Warrior max energy pool is 20, so at least it allows you to cast 25e spells...

I suggest this: https://guildwars.magical.ch/OQYTER5qWSpAJCYwUEUjmUVUAA

Precast Drunken Master in advance to get the energy back, precast Glyph of Essence to get energy back, then instant cast Meteor Shower at the beginning of the fight, thanks to Chimeric Prism!!1! Stonefist Insignia can make each meteor fall knockdown for 3s. You have time to build up Low Blow before the last knockdown wears off so you can do big damage + Cracked Armor with it, which sets up a Decapitate execution (cool note: you don't care about losing all your energy, you already did)

Resurrection Signet is just there because you have no energy to cast anything else anyway