His weapon was a tridant, with which he could make the earth shake, causing earthquakes, and shatter any object.
He was second to Zeus in power amongst the gods.
At birth Poseidon was swallowed whole by his father Kronos (Cronus), but Zeus later enlisted the aid of the goddess Metis who fed the Titan a magical elixir causing him to disgorge the god.
"POSEIDON - Greek God of the Sea & Earthquakes." Theoi Greek Mythology. N.p., n.d. Web. 05 Jan. 2017
"World Book Student | Article Page." World Book Student | Article Page. N.p., n.d. Web. 05 Jan. 2017.
Http://www.youtube.com/channel/UC_fzQHyIMzFsgZiK_XD1mNQ. "Poseidon - The Greek God Of The Sea." YouTube. YouTube, 20 Aug. 2015. Web. 05 Jan. 2017.