Lets just cut to the chase, Artorias is dead and we don't know why, and there are no remnants of the Abyss anywhere except for the ruins of New Londo. And with time being distorted in Lordran, this leads to the belief that the Chosen Undead already travelled back in time to free Artorias, kill Kalameet and stop the spread of the Abyss by destroying Manus, but in an alternate universe where all of that happened much earlier.
But I must say, I don't think the Chosen Undead 'stopped' the Abyss, but rather make it flee to New Londo (Bridge in the Valley of Drakes that connects Darkroot/Oolacile to New Londo). And this is where the Four Kings fall to dark and their knights were transformed to Darkwraiths. After every former knight of New Londo failed Kaathe (He may have fled along with along with the abyss after Manus' death because he may have played the role of tempting the citizens of Oolacile to awaken Manus), he then believed that the Chosen Undead destroyed Manus and moved the Abyss to a safer spot as a sign of his/her return as the Dark Lord. He then waited for him/her to destroy the Four Kings, which would make sense since the Dark Lord would be able to destroy them other than Gwyn or his army. Whoever destroyed the Four Kings other than them would be considered the Dark Lord by Kaathe.
But I must say, I don't think the Chosen Undead 'stopped' the Abyss, but rather make it flee to New Londo (Bridge in the Valley of Drakes that connects Darkroot/Oolacile to New Londo). And this is where the Four Kings fall to dark and their knights were transformed to Darkwraiths. After every former knight of New Londo failed Kaathe (He may have fled along with along with the abyss after Manus' death because he may have played the role of tempting the citizens of Oolacile to awaken Manus), he then believed that the Chosen Undead destroyed Manus and moved the Abyss to a safer spot as a sign of his/her return as the Dark Lord. He then waited for him/her to destroy the Four Kings, which would make sense since the Dark Lord would be able to destroy them other than Gwyn or his army. Whoever destroyed the Four Kings other than them would be considered the Dark Lord by Kaathe.