I updated the Savant to Level Up for the Adventures in ZEITGEIST book. As the others said, it's the 'person who fights with their mind but not with magic.'
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SAVANT TRICKS
The marquee mechanic for 'savants is tricks.' You have developed a small number of clever gambits, deft maneuvers, and canny guards which help you prevail in battle by using your wits. You spend your bonus action to prepare a trick, and then use that trick once (usually without needing to spend an action or reaction), after which you have to spend another bonus action to prepare a trick. At higher levels, you can choose one signature trick that you always have prepared, and can prepare a few tricks between rests without needing to spend a bonus action.
About one-third of tricks defensive abilities called 'aegises,' one-third are 'flourishes' that let you mess with an opponent you've hit, and one-third are miscellaneous.
If a trick offers a saving throw, after you use it against a particular creature, that creature has advantage on saving throws against other uses of that same trick until the end of combat. If the trick doesn’t permit a saving throw, after you use it against a particular creature, you cannot use the same trick against that creature for the rest of the combat.
For instance,
Improvised Bastion Aegis. When a creature’s attack, spell, or ability would damage you, you can use this trick to devise a momentary defense (using a chair as a shield, predicting a safe spot in an explosion, diluting a spray of acid with a solvent, etc). You gain resistance to one type of damage you would take, which protects you only against the triggering hostile act.
Serpentine Rush Aegis. When you are targeted by a ranged attack, you can use this trick and your reaction to move your speed. Until the end of your next turn, ranged attacks against you have disadvantage. Additionally, your movement might get you to a location where cover makes you hard or impossible to hit. Reduce your speed on your next turn by the distance that you move when using this trick.
Disarming Flourish. When you hit a creature with a melee attack, you can attempt to disarm it. If it fails a Strength saving throw, its grip is loosened, and the creature cannot make use of the item until it spends a bonus action or attack on its turn to regain a solid hold. If the creature has disadvantage on the save and fails both rolls, it drops the item.
Surgical Flourish. When you have advantage on a melee attack and both dice results are high enough to hit, choose one of the creature’s limbs or eyes to debilitate. If the creature succeeds a Constitution saving throw, you debilitate that body part until the end of your next turn. If it fails the saving throw, the body part is debilitated until the creature can take a short rest.
A creature cannot use a debilitated limb to attack, and cannot hold any items or effectively wear a shield with a debilitated limb. A creature with a debilitated leg has its speed reduced by half, it falls prone after using the Dash action, and it has disadvantage on Dexterity checks to balance. A creature with a debilitated eye has disadvantage on Wisdom (Perception) checks that rely on sight and on ranged attack rolls.
Frightful Suppression. When you make an attack that causes loud noises – a firearm or grenade, or also items and spells that deal thunder damage – you can use this trick to force the attack’s target (or creatures in the attack’s area) to make a Wisdom saving throw to gauge when it is safe to move, and thus avoid being pinned down. A creature that fails cannot move until the start of your next turn unless it spends an action.
Rallying Word. You know just what to say to inspire an ally’s flagging stamina. You can spend a bonus action to let an ally within 30 feet who can understand you spend a hit die. If it does, it rolls that hit die (adding its Constitution bonus) plus 1d8 and heals hit points equal to the total. The bonus dice increase to 2d8 at 5th level, 3d8 at 11th level, and 4d8 at 17th level. After you use this ability, the same ally cannot benefit from it again until you complete a short rest.
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As you level up you learn more tricks and can choose various ways to outwit foes. Like, at 2nd level you can choose between learning a small number of combat maneuvers (like what Fighters and other classes get in Level Up), or you can get the ability to use your reaction to try to disrupt the reactions of your opponents. The former could let you make a chatty swashbuckler like Inigo Montoya, while the latter could be reminiscent of the Robert Downey, Jr. version of Sherlock Holmes who is always a step ahead of his opponents.
You also get to choose your archetype, which determines what your greatest aptitude is. The book presents three types of savant: Steward, Vanguard, and Vox. The steward is expert at protecting and healing allies. The vanguard joins the thick of the fight, looking for tactical opportunities others miss. The vox deeply understands how words can manipulate people.
Do you want a character like Claire from Outlander? Make a steward. Want Ender from Ender's Game? Vanguard. Want The Doctor from Doctor Who? Pick Vox.