In appearance, Shamshel resembles a cephalopod-like creature around Evangelion-sized and normally seen in horizontally oriented posture whenever not engage in any fight. When it goes for battle, it changed it's posture to a vertically oriented "combat mode" and it's arms transformed into a pair of energy-imbued whip tentacles which can stab, slice and dice virtually anything like katanas.
Its skin is mostly purple with some pink sections underneath its large "head". The Angel appears to have two false eye spots on the top of its head composed of an inner black circle and outer yellow ring, but is obviously not sees through them. Also, the Angel's core is located on its torso just underneath its head with eight small, insect-like legs situated just below it.
Shamshel doesn't have much personality like Sachiel before it due to it mostly focused on searching for Lilith the second Angel within GeoFront. Even while being barraged by Tokyo-3's defensive emplacements, Shamshel was simply ignore them and uses it's AT-Field force field to protect itself. In spite of this, Shamshel would engage any lifeform which having the identical essence with Angels but is not Lilith (namely Evangelions) in more serious manner.
Unlike Sachiel however, Shamshel's approach when confronting Angel-based entities like Evangelion was in more aggressive manner where it mercilessly whipped Shinji's Evangelion Unit 01 after the latter waste his gun's ammo. The Angel even also sliced nearby buildings into dices that stood between it and Eva, and also reckless; It overestimate Eva's more aggressive attempt to killed it with a Progressive Knife where it counteract by spearing the Eva's abdomen, but forgot to increase the density of it's AT-Field that resulting it's demise with it's core impaled.
Neon Genesis Evangelion
Shamshel made it's appearance known as it passed over the ocean and makes landfall at Odawara before heading for Tokyo-3, easily passing through all defensive emplacements simply by having them struck its AT-Field alone and not retaliate any of their attacks. This forces NERV to sent Shinji with his Eva. Unit-01 to intercept it. Shinji tries to shoot Shamshel with his Pallet Rifle, but much to Misato's frustation, he fails to neutralize its A.T. Field and only ends up obscuring the target with smoke. Just as he cease-firing, Shamshel immediately disarmed the Eva's Pallet Rifle by sliced the weapon into two and sliced the nearby building into two in process like a katana.
Because Shinji was overwhelmed by fear, which prevent him for taking another deployed gun and chooses to flee instead, allowed the Angel to immediately chasing his Eva whilst slice and dice anything that stood on its way. It managed to struck the Eva and sliced it's power cable off, resulting it would deactivates in 5 minutes due to the loss of power cable caused it to activated the emergency battery. Worse it tossed the Eva high into the air, right into on a nearby mountainside where Kensuke and Toji hides to watch the battle. The Angel tries to deliver a final blow, but is stopped by Shinji by having his Eva grab it's tentacle before allowed both boys to entered the cockpit plug and tosses Shamshel aside.
The Angel quickly recovers and prepares for counterattack just as the Eva recklessly goes for it with a progressive knife brandished on the right hand. Shamshel tries to stop its reckless opponent by stab the Eva on abdomen, only for unexpectedly have it's core impaled, cracking it. The process ultimately resulting it's death almost at the same time the Eva ran out of power. Shamshel's body was left behind as an almost fully intact specimen of an Angel.
Rebuild of Evangelion
Shamshel's role is more or less same, but the difference were it's appearance and it's fate.
When Sachiel dies, the core puffs up and the whole Angel explodes in a rain of blood-like fluid, leaving behind only the whips impaled in Unit-01.