Topo is a friend of Aqualad's from the Conservatory of Sorcery.
Topo is shy and timid, and does not like attention. He is not much of a fighter, a feature that made him an easy target.
Topo is an anthropomorphic squid. His skin is gray with spots, and he has three fingers on each hand. His lower facial features, including mouth, are hidden behind six short tentacles.
He wears a black and dark blue tunic with bright blue markings.
Topo was finishing a magical mosaic mural of how
Garth and Kaldur'ahm saved Aquaman from Ocean-Master when his old friend, Kaldur, arrived. He showed his work, which was animated with his magic.
Topo was attacked by
purists. He tried his best to escape, even spouting ink to cover his retreat. But it was to no avail; the purists found him and branded "MIΓAΣ"—impure—into his chest.
He was ashamed of his mark, and did not like showing it. He only showed it after Kaldur insisted.
King Sha'ark blamed Topo for being an easy target.
Poseidonis September 6, 19:27 UTC-2
Topo's friends knew full well what caused his injuries, and they sought out
Ronal and his friends. As the argument grew hotter, Topo moved to the background. For him, it all wasn't necessary. The fight was broken up by Aqualad, and all returned home.
Topo did not join his friends to overturn a purist ambush on Aqualad and his teammates, but did go to the trench. When a mysterious spell weakened all the impure Atlanteans, Topo was affected too. He still had the wits to spout an ink screen to save King Sha'ark from a certain death. When the ink had cleared, the purists were defeated, though Topo was too weakened to continue the fight.
Poseidonis September 7, 07:01 UTC-2
Ronal was fully pardoned for his complicity in the abduction of Queen Mera, Topo successfully persuaded Sha'ark not to eat him.
Atlanteans, although Atlantean attributes: human, have through scientific and sorcerous means developed several abilities which allow them to live comfortably under the sea: 
Breathe underwater: All Atlanteans are capable of surviving the aquatic atmosphere under the sea. Some accomplish this without the presence of visible gills.  
Temperature resilience: Resistant to low temperatures and the effects of freezing,  although notably hindered by high temperatures.  
Durability: Dense flesh, although not invulnerable.    Strength: Ranging from undetected levels to super strength.   
As a student of the Conservatory of Sorcery, Topo was skilled in Atlantean magic. He uses his skills for art rather than combat. Sorcery:  Ink spout: One of the features of his cephalopod biology. 
Topo has been a supporting character of Aquaman since the 1950s. Originally just an octopus, more recent appearances make him an anthropomorphic squid.
This is his first animated appearance.
Weisman, Greg (2012-02-02). Question #14113. Ask Greg. Retrieved 2012-02-03.
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Weisman, Greg, Kevin Hopps (w). Jones, Christopher (a). Atkinson, Zac (col). Sienty, Dezi (let). Chadwick, Jim (ed). " Under the Surface..." Young Justice 14 (March 21, 2012), New York, NY: DC Comics
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Hopps, Kevin (writer) & Oliva, Jay (director) (March 4, 2011). " Downtime". . Young Justice Season 1. Episode 8. Cartoon Network.
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Weisman, Greg, Kevin Hopps (w). Jones, Christopher (a). Atkinson, Zac (col). Sienty, Dezi (let). Chadwick, Jim (ed). " ...Here There be Monsters" Young Justice 15 (April 18, 2012), New York, NY: DC Comics
Dubuc, Nicole (writer) & Oliva, Jay (director) (November 4, 2011). " Failsafe". . Young Justice Season 1. Episode 16. Cartoon Network.
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Weisman, Greg (writer) & Oliva, Jay (director) (November 26, 2010). " Independence Day". . Young Justice Season 1. Episode 1. Cartoon Network.
Pugsley, Tom (writer) & Chang, Michael (director) (February 18, 2011). " Denial". . Young Justice Season 1. Episode 7. Cartoon Network.
Robinson, Andrew (writer) & Berkeley, Christopher (director) (September 16, 2011). " Targets". . Young Justice Season 1. Episode 10. Cartoon Network.
Hopps, Kevin (writer) & Divar, Tim (director) (Originally released on iTunes on October 14, 2012, broadcast on January 5, 2013). " Before the Dawn". . Young Justice Season 2. Episode 10. Cartoon Network.
Hopps, Kevin (writer) & Chang, Michael (director) (October 14, 2011). " Revelation". . Young Justice Season 1. Episode 14. Cartoon Network.