The Eldar only have access to one dedicated transport, but we can’t complain much about it because the new Wave Serpent is amazing. For years, I complained about the Wave Serpent because of its extremely high price compared to its firepower. I was in favor of lowering its cost, but the new codex went the other way: it still costs a lot, but it brings a battle tank’s firepower.
The Wave Serpent is a fast skimmer tank with armor 12 on the front and sides, making it one of the faster, more resilient transports in the game. It can carry up to 12 models, which is nice as it means you can carry a full squad as well as a character (something Space Marine transports have lots of trouble with). The Wave Serpent, like all Guardian crewed vehicles, is now BS 4, which is a really nice upgrade. It comes with twin-linked shuriken cannons on the turret, but can upgrade to scatter lasers, starcannons, bright lances, or missile launchers (which are once again absurdly expensive compared to the alternatives). It can also replace its underslung twin-linked shuriken catapult with a shuriken cannon, which I strongly suggest as it really augments the firepower of this transport. All of the above (except for the increased BS) is the same as in the last codex, though the costs of the weapon upgrades have dropped, so what makes the new Wave Serpent so good?
The answer is the serpent shield, which reduces all penetrating hits against the Wave Serpent to glancing hits on a 2+. This is a pretty awesome defensive upgrade, since it means that your enemy will have to take away all 3 hull points with little chance of a lucky explosion to kill the Serpent early or weapon destroyed/immobilized results to reduce its effectiveness.
But that’s not all! If you sacrifice its defensive abilities for the next turn, you can fire the shield at the enemy, and it’s way better than you’d expect. It fires D6+1 S7 shots that ignore cover, making it great for taking out light to medium vehicles (nothing kills Wave Serpents as well as other Wave Serpents) and light infantry hiding in cover. With its massive number of shots, the Wave Serpent is even able to threaten heavy infantry by forcing a ton of saves.
The most common and arguably best loadout for the Wave Serpent is with twin-linked scatter lasers, a shuriken cannon, and holofield (which add +1 to its cover save as long as it moved). This means that it almost always has a 4+ cover save and can fire 9-14 S6-7 shots. As long as one of the scatter laser shots hit (which they almost certainly will), all the other shots are twin-linked. That is a ton of extremely reliable firepower. It can even engage flyers, as that number of twin-linked shots will certainly land a few hits.
This is not to say that only scatter lasers should be taken. While they provide a great benefit in twin-linking the other weapons, they leave the Wave Serpent unable to deal with AV13-14 targets. I’ve been running lists that rely on Wave Serpents for anti-tank, and found that they really can’t deal with heavy tanks like Predators, Leman Russes, and Annihilation barges unless they have bright lances. If you have other lances in your army, then you can stick to scatter lasers on Wave Serpents. If not, a few bright lance armed Wave Serpents will likely win you battles.
As a final note, there is a substantial trade-off involved in whether you fire the serpent shield or not. In my experience, it is almost always worth firing the shield and sacrificing its defensive benefits. It is that good of a weapon. Defensively, the shield is great when you go second, meaning it mitigates the damage that you take from your enemy’s first turn shooting (during which you don’t get a Jink save). Also, if you have a squad that you really need to get into position quickly, it is very worthwhile to keep your shields up. A turbo-boosting Wave Serpent that reduces most hits to glancing will be very hard to destroy before it delivers its cargo. This will mostly apply to Wave Serpents carrying short ranged but very destructive units, such as Fire Dragons or Wraithguard.