Ramiel is the Fifth Angel, and assaults New Tokyo-3 from the direction of Lake Ashino. Its physical form is that of a giant octahedral floating object with highly reflective planes. Other than its shape, it lacks any distinguishing physical features.
With its Core hidden deep inside its body, an exceptionally powerful AT Field, and a devastating long-range particle beam, Ramiel is among the most powerful Angels. Offensively and defensively the Angel is perfect, a genuine flying fortress as described by NERV Operations Director Misato Katsuragi.
Upon its arrival at New Tokyo-3, Evangelion Unit-01 is dispatched to intercept it. However before the construct is even able to get off the elevator, it is attacked by Ramiel's particle cannon. In an instant the beam melts through three layers of Evangelion Unit-01's chest armor, sending its pilot Shinji Ikari into cardiac arrest.
As Evangelion Unit-01 is retreated and Shinji undergoes medical care, further attempts to attack the Angel using long-range mortar bombardment prove futile. Not only is the Angel's AT Field impenetrable, but its long-range particle beam is capable of incinerating any target with a single shot.
After incapacitating Evangelion Unit-01, Ramiel proceeds to drill from New Tokyo-3 into the Geo Front. The Angel's only weakness proves to be the fact that it is very slow to penetrate the many layers of armor protecting the Geo Front. It took nearly ten hours, during which NERV Headquarters had enough time to devise a counter-attack. Had it not been for this long delay, there is no doubt that Ramiel would have been able to destroy NERV Headquarters and possibly cause the Third Impact.
The counter-attack against Ramiel took the form of Operation Yashima, which called for the use of a long-range sniper attack using the Strategic Self Defense Force's latest Prototype Self-Propelled Positron Cannon. In order to penetrate the Angel's AT Field from a distance however, massive amounts of electricity was needed, which was rerouted from across Japan.
With Evangelion Unit-00 in charge of defense and Evangelion Unit-01 as the gunner, Ramiel is ultimately defeated as its AT Field is pierced and its Core is destroyed. The Angel does however manage to inflict extreme damage to Evangelion Unit-00.
Ramiel has gone through significant changes in the 2008 feature film Evangelion: 1.0 You Are (Not) Alone, the biggest of which is that the Angel's shape is no longer static. Its body is now highly polymorphic and capable of reshaping around its central Core to accomplish numerous tasks. It also behaves more alive, shrieks when harmed and literally explodes into an unfocused crystal star formation when panicked.
Ramiel's impressive capabilities are still tied directly to its exceptionally powerful AT Field, and its polymorphic body reshapes depending on how its AT Field is to be projected, either offensively or defensively. While its default shape is still octahedral, it has been observed in a ring shape for wide area-of-effect damage, a solid hexagon shape for focused single-side defence, and a star shape for a massive single-target attack.
In addition, Ramiel now exposes its Core during various stages of polymorph, and part of the strategy to destroy it now involves a diversionary assault to expose its Core while Evangelion Unit-01 attacks using a long-ranged beam cannon. Ramiel also no longer uses a simple drill to penetrate the Geo Front, and instead moulds the southern tip of its body into an AT Field-based drill.
In the film Ramiel's death is also slightly different. Shinji Ikari no longer misses as a result of crossed weapons fire. His initial attack hits Ramiel's Core, but does not destroy it. Though injured, Ramiel responds with a massive focused-target attack that obliterates the entire mountain side. Fortunately, Shinji Ikari and Evangelion Unit-01 recover, and while protected by Evangelion Unit-00, manage to destroy Ramiel with a follow up shot.
Lastly, in the film Ramiel is classified as the sixth Angel instead of the fifth.