Chimera
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The Chimera Armored Transport is the Imperial Guard's main troop carrier, capable of transporting troops on the battlefield and giving them fire support.
Unlike the Rhino Transport of the Space Marines, the Chimera is less of an Armored Personnel Carrier and more of a Light Tank that happens to have transport capability an Infantry Fighting Vehicle, an infantry transport designed to transport men to where they need to be, then provide support fire and cover behind its armor. Remarkably survivable from the front and equippable with a wide array of weaponry, it has at least as much Infantry-killing firepower as 2 guard heavy weapon teams, as well as the ability to act as a mobile firepoint for guardsmen with Special Weapons that can shoot out from the vehicle. Adding both survivability and flexibility to an army that otherwise tends to be sluggish, the Chimera is a ubiquitous presence that finds a home in many Imperial Guard Army Lists.
Overview
The Chimera is one of the most important vehicles in the Imperial Guard's arsenal: it is a fast moving, amphibious vehicle capable of traversing terrain that even a Leman Russ would find impossible to cross (swamps, marshes and even the occasional river). When the enemy neglects to defend these positions because of their perceived obstructiveness, they can expect a squadron or two of Chimeras in their flanks or rear.
The Chimera has several uses: it can be an armored taxi of sorts where it rushes in between the front lines to insert and/or pick up units, and it can go to the rear to pick up new units and deliver them to the heart of the battle. If needed they can serve as moving barriers, providing troops cover while they engage the enemy. A third use is that they rush towards the enemy, shrugging off small arms fire as they deliver their payload into the most defended positions. The Steel Legions of Armageddon, one of the chief manufacturing planets for the Chimera, are fully mechanized and can move across the ash planes of their home world at frightening speeds.
The Chimera can mount a variety of weapons to support the squads they carry. The most common weapon associated with the Chimera is the Multilaser, a larger, rapid-fire version of the Lasgun, used to suppress enemy movement. This turret weapon can be replaced with a Heavy Bolter or a Heavy Flamer, and can field either of those two in its hull. Forge World gives the Chimera even more blasty power with the ability to replace the main gun with an Autocannon, turning it into a different breed of threat altogether. Each side of the tank features a row of three Lasgun turrets that embarked passengers may fire at enemy squads. For added punch against vehicles, it can also mount a Hunter-Killer Missile.
However, probably due to the current Imperial Guard Codex, not so many Guard players use them, preferring the SIGAOD (Shooty Imperial Guard Army Of Doom), which is better supported by the Imperial Guard's other transport, the Taurox.
Rules of Note
There are actually written rules that say this particular Metal Box is also a boat. Its Amphibious rule allows it to move across water terrain. This would mean that it could ram an Ork Submersible, or tank shock a Saharduin squad. Sadly, since nobody uses water terrain, plays apocalypse, or has more than one Saharduin model, Amphibious is a totally useless rule.
Another rule of note is the one that lets you use orders whilst riding in a chimera