Both Exal Kressh and Darth Wredd were enslaved by their masters, blindly lashing out like the animals they were reduced to. Both attempted to break free of these shackles by forging alliances with their traditional enemies, but instead of truly freeing themselves, they simply lashed out at their erstwhile former comrades. Instead of achieving self-actualization, they knowingly followed a path of nihilistic self-destruction. Ultimately, the damage done to them by their masters was irreversible, and the only victory they could hope for was death.
Exal Kressh was the primary antagonist of The Old Republic webcomic series Blood Of The Empire, published in 2010. She is also mentioned in The Old Republic Encyclopedia. Darth Wredd is the primary antagonist of the Legacy Volume II comic series, published from 2013 to 2014. Further information is provided in the Legacy Handbook Addendum, featured in the fourth trade paperback, titled Empire Of One.
I also think I should offer my response to the Battle of the Floating World, and whether or not it constituted a true and total extinction of the Sith. Short answer, no. All of the established Sith characters who survived the Legacy series proper, namely Darths Nihl, Talon, Maladi, and Havok, are unaccounted for. And to be frank, it's doubtful that they would have shown up at the battle, anyway. While I will concede that the overwhelming majority of the One Sith Order was exterminated, a total extinction is unlikely. If anything, Wredd probably did Nihl a favor, as Nihl had effectively fallen into his position as Acting Dark Lord, and didn't command the same level of respect as Darth Krayt. While Krayt's surviving inner circle could be trusted to place the idealogy ahead of their ambitions, betrayal within the rank and file was practically inevitable, as Darth Wredd himself demonstrated.
10:45 - The Old Republic Encyclopedia, pg 256, Sentient Species - Sith Purebloods
11:09 - The Old Republic Encyclopedia, pg 171, Legacy of the Sith - The Kressh Legacy
11:37, 11:53 - The Old Republic Encyclopedia, pg 220, Smuggler: Weapons and Armor - Armor and Fashion
12:50 - The New Essential Guide to Alien Species, pg 80, Human
14:08 - Legacy Era Campaign Guide, pg 183, Imperial Knight - Imperial Knight Armor
14:16 - Darth Vader: A 3-D Reconstruction Log, pg 6, Collar/Chest Armor - Shoulder Armor
17:47 - The Jedi Path, pg 145, History of the Sith
17:51, 18:49 - The Jedi Path, pg 67, Lightsaber Forms, Form II Lightsaber Combat: Makashi
18:09, 18:53, 21:57, 23:13 - The Jedi Path, pg 74-75, Lightsaber Forms, Form VI Lightsaber Combat: Niman
18:17 - Hero's Guide Web Enhancement, Variant Lightsaber Forms
18:21, 19:15 - The Jedi Path, pg 136, Advanced Lightsaber Techniques, Form VII Lightsaber Combat: Juyo
19:08 - Star Wars Insider 62, article - Fightsaber: Jedi Lightsaber Combat
22:24 - Legacy Era Campaign Guide, pg 169, Influential Personalities - Darth Krayt
29:05, 29:18 - Darth Bane: Path of Destruction, Chapter 11
29:43 - The Old Republic: Fatal Alliance, Chapter 39
31:59 - Book of Sith, pg 96, Dark Side Combat - Crucitorn
32:40 - The Old Republic: Deceived, Epilogue - Dark Lord: The Rise of Darth Vader, Chapter 11
33:21 - The Jedi Path, pg 129, Alter Abilities