Four pieces of plasteel armor—helm, body armor, gloves, and boots—are added in the Jedi patch for SLASH'EM (incorporated into the variants Slash'EM Extended and SLASHTHEM and available as an independent patch). These make up the iconic armor of the stormtrooper and, along with a heavy machine gun or submachine gun and ammunition, are part of their automatic starting inventory in the patch.
Plasteel is a fictional material from the Star Wars series. It is, as its name suggests, a compound of plastic and steel. More precisely, it is a plastic reinforced with the fictional alloy durasteel. The Imperial Stormtroopers' armor is made of thin plates of plasteel, lightweight but providing adequate protection against physical damage.
Plasteel is also the name of a durable steel compound in the Dune universe, as well as a real-life composite of steel and fiberglass used to make automobile chassis.
|[ plasteel helm|
|Base price||20 zm|
The plasteel helm has a natural armor class of 3, one point more than the best non-magical helm, the dwarvish iron helm. However, the plasteel helm covers the entire head and lacks a visor, which imposes some restrictions on its wearer.
While wearing a plasteel helm, you cannot:
Also, players polymorphed into (master) mind flayers will find that they will not be able to wear a plasteel helm because it will not fit over their tentacles.
|[ plasteel armor|
|Base price||80 zm|
Plasteel body armor has a natural armor class of 6, equivalent to splint mail, banded mail, bronze plate mail, or the dwarvish mithril coat, but weighs significantly less than any of them—with the exception of the dwarvish mail, which weighs the same. Being made of plastic, it interferes less with spellcasting than any of these armors, but it does not provide any magic cancellation.
|[ plasteel gloves|
|Base price||25 zm|
|[ plasteel boots|
|Base price||25 zm|
As a general rule, all types of plasteel armor offer a respectable armor class with a relatively low weight, no interference with spellcasting (except in the case of the body armor, where it is less than most alternatives), and no danger of rust or corrosion (though there is the possibility of fire damage from wands of fire, fire elementals, etc.) However, plasteel armor is not likely to be part of a player's ascension kit wish list, because it is only found on stormtroopers, who are only found on the Jedi quest (except in Slash'EM Extended, where they may be randomly generated), and even if it can be found, there are better options.
Jedi will find plenty of plasteel armor from the many stormtroopers they fight during the quest, but not all of it will be useful to them. The body armor will be useless to the Jedi, until late in the game when the penalty for wearing body armor other than a robe can be ignored, and even then the Jedi will probably have found some dragon scale mail, which offers a higher armor class (nine versus six) plus a needed extrinsic like magic resistance or drain resistance. Players other than Jedi who find plasteel armor in a game that includes the Jedi patch (e.g. in Slash'EM Extended) might want to hold onto the body armor if they do not yet have crystal plate mail, a mithril-coat, or dragon scale mail, but only if no better options are available.
As for the other pieces, the helmet, boots, and gloves might be useful to Jedi, as an upgrade on a dwarvish iron helm, iron shoes or high boots, and leather gloves, respectively. But they will probably want to trade them off for magical alternatives (e.g. helm of telepathy, boots of speed or water walking, gauntlets of dexterity, etc.) as soon as those become available, unless a few extra points of armor class are desired more than extrinsics.
In summary, plasteel armor is a good nonmagical choice for any armor slots you haven't been able to fill with your desired magical items, but it is probably not useful enough to change your ascension kit wish list.
Reference: Benjamin Schieder's Jedi Patch