Origin

After Atlantean warriors were killed while trying to defend the seas from an illegal Roxxon whaling ship, Namor decided to enlist a number of aquatic superhumans to join a team of champions to wage war on the surface world.

Creation

The Defenders of the Deep first appears in Avengers (2018) #9 by Jason Aaron and David Marquez

Major Story Arcs

War with the Surface World

The first targets that Namor led the Defenders against is:

• Russian subs in the Black Sea, which brings them into direct confrontation with The Winter Guard
• Roxxon oil rig in the Gulf of Mexico, which brings them into direct confrontation with The Squadron Supreme of America.

Although Namor planned for very specific targets, his Defenders thirsted for war. While contemplating the future of his team, Namor was chosen by the Phoenix Force to compete to become the new host. He led the team to the island The Phoenix had landed on, just outside the Avengers Mountain. They would symbolically stand guard, occasionally trying to fight members of the Avengers and their allies.

Namor was ultimately embarrassed in the tournament, having all the salt water Phoenix punched out of him. This, as well as his embarrassing attempt to turn surface dwellers into water breathers and an attempt by Russia to destroy Atlantis, inspired the Defenders to abandon their adoptive country.

War of the Seven Kings.

After Namor's failure and imprisonment, the War of the Seven Kings erupted, as seven would-be royals fought for Namor's throne. During this period, the Defenders of the Deep scattered.

• King Crab and Manowar were hired by Attuma to kill Namor, who easily defeated them
• Orka turned a sunken SHIELD helicarrier into an offensive whale slaughterhouse
• Tiger Shark leads pillagers against the wild depths.