Board Thread:General Discussion/@comment-27984457-20160922193051/@comment-27701762-20160923193625

Alkhor-dm wrote: My opinion: there was enougth 6 (Azriel use 6 and sucsess) and Azgor jast can not use souls (in other case he acsept Toriel's plan about only 1 soul) and tells everyone about 7 jast becouse try to get some time for himself (and meanwhile tells his scienist make research about vessel, that choul hold souls and use it, when time comes) Asriel has the equivalent power of 7 human souls. He has the 6 human souls, plus the souls of nearly every monster in the Underground, which is stated to be equal in power to one human soul.

And the Barrier is stated to have been created by the 7 most powerful human sorcerers. The need for the power of 7 human souls is meant to counteract the power that originally made the Barrier.

Asgore doesn't absorb the souls, or follow through with Toriel's plan (it is never stated that she told the plan to Asgore before she left), because he wanted to prevent violence in the first place. He didn't want to kill anyone, and was forced into a corner by his own decree. His hope the entire time was that no more humans would fall into the Underground so he would never have to make good on his command.