His specialty is to create and manipulate clay and forms it into different animal-shaped explosives. to attack his opponents with. The clay is infused with chakra and is detonated from a remote distance by Deidara, using the command "Katsu", which translates into "Detonate".
The means to make this explosive clay are the mouths in the palm of each hand. All he has to do is devour an animal or anything for that matter and he is able to copy its form. And like said he's able to bring it to life by infusing chakra into the molded clay. Depending on how much chakra is infused he refers to his creations from anywhere between "C1" to "C4", C4 being the strongest.
Deidara was recruited after being noticed by Akatsuki's leader, Pein, as a successful terrorist bomber. Originally Deidara refused to join Akatsuki, but after being defeated by Uchiha Itachi he was forced to join. From that point on Deidara is determined to defeat Itachi, and searches for a way to resist Itachi's genjutsu. During his time with Akatsuki, Deidara was first teamed up with Sasori. Sasori having a somewhat artistic ability himself earned the respect of Deidara, who always addresses him as master Sasori. After Sasori is killed, he's paired with Tobi, a relatively young boy who tends to unintentionally irritate Deidara a lot. Despite that, Deidara tries to protect Tobi, and treats him as a disciple.
Deidara is also the one who starts the assault on the Sand Village in order to abduct the Kazekage, Gaara. He succeeds in his mission and was able to obtain the jinchuuriki Gaara. He's a long distance fighter and isn't partically good at taijutsu as shown in his fight with Gaara. His long range attacks however are very damaging, and since he's not your average head-on attacker he's one Akatsuki member you do not want to underestimate. During his fight with Gaara, Deidara loses one hand, but was able to revive it later on. Although the arm he lost escaping Kakashi's Mangekyou Sharingan technique wasn't revivable, it was lost forever.
Just like Sasori was able to turn himself into a puppet, Deidara is able to turn himself into a human bomb. Just like on his hands, he has a mouth on his chest which can be unsealed. Once unsealed and provided with clay he can turn himself into a living bomb which can destroy everything in a 10 kilometer radius. He eventually uses this technique as a last resort in his fight against Uchiha Sasuke in an attempt to prove his art is absolute. Deidara hated the fact that it was Sasuke, and not him, who eventually killed Orochimaru and tries to end the fight in a draw. However, Sasuke was able to survive and Deidara just ended up blowing himself up. Deidara first appears in episode 135 stating that the Akatsuki would eventually kill Orochimaru.