Ultimate Deathknight was released in Raid Shadow Legends as a free Legendary login reward champion in August 2022 following a huge marketing campaign showing the original Deathknight desperate to ascend to greatness!
Ultimate Deathknight has a solid kit that will help players progress through Dungeons, especially Ice Golem and Spider. His AOE Decrease Attack ability is a really powerful ability in both of these dungeons and his team shield mechanic is also powerful to help sustain the team. Those same abilities will also be useful in early Clan Boss and Hydra Clan Boss.
One of the most interesting parts about his kit is a passive with the ability to block single target damage and transfer it to Ultimate Deathknight. This is really cool against spiderlings to ensure the damage is always directed at a tank. The same passive could be put to good use against single target hitters in Arena such as Rotos or Mountain King and no doubt will be used in Doom Tower waves against nasty opponents.
Ultimate Deathknight will have some good use cases in Doom Tower specifically against the Magma Dragon where he can provoke and protect the main target from damage & The Scarab Boss where his shield will help to overcome the provoke debuffs.
Books are certainly valuable in his A2 and A3 abilities reducing cooldowns and improving those skills but it is worth noting he is not the best Legendary in the game and will be used less and less towards end game. A more realistic end game build will be to use him to solo Dragon 25 & Ice Golem 25 with specific Niche builds (toxic gear & specific masteries see video below) or as an Arena Specialist.