Matarael is the Ninth Angel, and is often considered by fans to be the weakest of the Angels (this may however be unfair).
Its physical form resembles that of a giant spider, albeit with only four legs. Its main body is rather small when compared to other Angels, and is covered by organs that resemble eyes. Its giant yet thin legs make up the rest of the Angel's physical form.
Matarael arrives at New Tokyo-3 during a massive power outage that leaves the city and NERV Headquarters defenseless. The Angel casually walks into the city unchallenged. An interesting fact about this encounter as fans often point out; when left unchallenged, the Angel does not directly attack the city, and in fact poses little threat to the civilian population. This is often seen as significant fore-shadowing as to the true intentions of the Angels.
After enjoying the sights of New Tokyo-3, Matarael locates a vertical shaft that leads down into the Geo Front. It then begins to excrete a highly corrosive acid into the shaft, burning and dissolving through the many layers of armor.
Although the acid proves formidable, causing considerable damage to Evangelion Unit-02, the Angel displays no other means of attack. Because of this it is often considered among the weakest of the Angels, however this could simply be because no opponent has ever challenged it on the surface (not even the U.N. Forces or the Strategic Self Defense Force).
One might consider for a moment Ramiel, the Fifth Angel. Had it not been confronted on the surface by Evangelion Unit-01, the true power of its AT Field and its beam cannon would have remained unknown. Judging by how an Angel attempts to enter the Geo Front (Ramiel drilled for ten hours), may not be the most accurate way of ascertaining its true capabilities or its potential for destruction.
Regardless, the same vertical shaft that Matarael was assaulting was being used by the Evangelion Units to make their way to the surface. By working together, Evangelion Unit-00, Evangelion Unit-01, and Evangelion Unit-02 ultimately defeat Matarael by neutralizing its AT Field and shooting several hundred rounds of rifle fire through the Angel's body.