Iruel

Iruel is an "angel of fear".
His appearance is in episode 13, marking a special point in the angels strategy, because he nearly reaches the central dogma and attacks Nerv.
Iruel appears to be a small virus. During a test of the dummy-plug system, a fast spreading corrosion in the compounds walls finally infects the Evangelion test-bodies. He couldn't be stopped, and infects the > Magi-computer. In there, Iruel soon defeats Melchior and Balthasar. He then tries to initiate self-destruction, but Caspar refuses.
Ritsuko slows the synchronisation between the three computers, buying them some additional time, then she enters Caspar and reprogrammes her according to the current attack.
Iruel is finally defeated by Caspar.