The Fire Prism Grav-Tank

The only bonified BFG in the Eldar Arsenal. With a range of 60 inches and Crystal Targetting Matrix you can fire midway through the movement phase, decimate some unsuspecting vehicle, then duck back behind cover before anyone is the wiser. It uses a blast template so it can work great against GROUPS of targets- bikes, land speeders, clustered bugs, etc.

Anything on a Warhammer 40k table that even looks like a big gun is going to draw a lot of fire, but there are some things you can do to keep your Fire Prism intact long enough for it to hit something.

Moving more than 6 inches will keep all hits on your Fire Prism glancing and moving less than 12 inches will allow you to shoot one weapon (all you really need, right?). So always move your Fire Prism between 6 and 12 inches. If you have the Crystal Targeting Matrix option, stop in the middle of that move, fire, then complete your move- hopefully to a partially hidden (hull-down) position.

For extra protection, especially on boards without a lot of cover to hide behind, a holofield will force your opponent to roll any damages twice and use the lower of the two results on the damage table. Crew Stunned and Crew Shaken results can be either ignored or lessened if you add the Spirit Stone option.

With all the protective options, the Fire Prism can be expensive but it usually only needs two well-placed hits to be worth it's points. To help you obtain those well-placed hits, a nearby Farseer with the Guide ability can let your Fire Prism re-roll a missed shot.