"The faithful messenger of God. He descends from the Heavens under the command of God to bring about news of fortune or ill news. He commands us to heed his warnings of dire happenings. It is he that spreads the truth. And it is he that is tasked with appearing before the prophets of God."
In Abrahamic religion (which encompasses Christianity, Judaism and Islam), Gabriel is a high-ranking messenger angel. His/her name means "Master who is of God" and is known to be the left hand of God and the embodiment of the Holy Spirit, in contrast to Michael who is the right hand of God.
To Christians, his/her primary task is that of a messenger who told Elizabeth that she would bear John the Baptist and Mary that she would bear Jesus, meaning he/she is remembered each Christmas/Advent as the messenger of the Annunciation or Immaculate Conception (it was also Gabriel who asked Mary to name her son Jesus, meaning "savior".)
He/she is also mentioned as announcing the prophecy of seventy weeks to Daniel and is also recognized as St. Gabriel, the patron saint of communications workers. By Muslims, he is especially noted for revealing the Qur'an to Muhammad and for being the messenger that tells prophets of their obligations. In Islam, Gabriel is the highest-ranking angel, while Raphael is the second. He is also called the Holy Spirit in Islam.
Out of all the angels, Gabriel deeply loves the humans and spends the majority of his time living among them. However, after the fall of Lucifer and the absence of God, Gabriel made his residence on Earth seemingly permanent. He will, silently, protect the humans he walks amongst whenever they are threatened. In human form he is laid-back, jovial, humble, and an eccentric. However, he shows a deceptively cunning and serious side when the situation warrants it, and unlike his brothers, Gabriel is actually sarcastic and humorous when he needs to be, making him the most 'human' of the angels.
Gabriel is known to be a trickster among his brothers, however, he does not lie. He has immense knowledge and understanding of the flow, application, and consistency of magical energy. Among his brothers, he is the most proficient in using spells and attacks, and can even use multiple ones in conjunction for various combination and diversion tactics. Lucifer even admitted that Gabriel is unpredictable.