Deduction and Reasoning
3rd level Investigator feature
When you choose this subclass as your Field, you gain proficiency in Insight and Investigation, and your proficiency bonus is doubled for any check you make with either skill. If you are already proficient in these skills you gain proficiency in another skill from the scholar skill list.
Your intuitive nature grants you the following benefits:
Whenever you would make a Wisdom (Insight) check, you can make an Intelligence (Insight) check instead.
You have advantage on any ability check you make to detect illusions, shapeshifters, or if a creature is lying.
You gain a bonus to your Passive Perception equal to your Intelligence modifier (minimum of +1).
Private Eye
3rd level Investigator feature
You use your intellect to analyze and study your foes, improving your Field Research even more than before. As a bonus action, you choose and concentrate on one creature you can see within 60 feet of you and select it as your Mark.
When you hit your Mark with an attack or spend 1 minute observing it, you learn one characteristic about it of your choice: the creature's hit point maximum, armor class, a certain ability score, speed, Devil Fruit (if any, and only the type (Zoan, Paramecia, Logia)), haki (if any), class levels (if any).
You can use your Intelligence modifier in place of your Strength or Dexterity for weapon attack and damage rolls against your Mark.
You can make an Intelligence saving throw, in place of Constitution, to maintain concentration on your Mark.
Your weapon attacks against your Mark score a critical hit on a 19 or 20.
The creature remains your Mark for up to 10 minutes, ending early if the creature becomes hidden from you, if you lose your concentration, or if you use this feature on another creature. Only one creature can be the target of your Mark at a time.
Deductive Expert
6th level Investigator feature
You always seem to be one step ahead of your foes. So long as you aren't incapacitated, you have advantage on any ability checks or saving throws that your Mark forces you to make. Your mark no longer requires concentration.
Additionally, when you roll initiative, you can use your reaction immediately to do one of the following.
Use Private Eye to Mark a creature you can see.
Make an Intelligence ability check to recall information.
Take either the Help, Ready, or Search action.
Ear to the Ground
6th Level Investigator Feature
Your line of work has granted you a unique familiarity with the underbelly of civilized society. Once you spend a long rest in a settlement, you have advantage on any ability checks you make to gather information on that settlement and its culture, active factions, or important figures.
Finally, if you spend at least a minute talking with your Mark, you can force it to (unknowingly) make a Wisdom saving throw against your Investigator save DC. On a failed save, your Mark cannot willingly lie to you for the remainder of that conversation.
Potent Insight
13th level Investigator feature
You know your mark inside and out. Your weapon attacks against your Mark are a critical hit on rolls of 18-20. Moreover, as an action, you can predict your Mark's next move and alert your allies to its plans. Until the start of your next turn, your Mark has disadvantage on all ability checks, attack rolls, and saving throws, and creatures of your choice have advantage on any saving throw your Mark forces them to make.
Once you use this feature you must finish a short or long rest before you can use it again.
Perfect Sleuth
17th level Investigator feature
Your sense for the truth has reached near-supernatural levels. You gain Truesight in a 60-foot radius.
Additionally, you can now target up to two creatures at once with your Mark, only selecting them one at a time. When you, or a creature you can see, hits your Mark with a weapon attack, you can use your reaction to turn that attack into an automatic critical hit.
Once you use this feature to turn a hit into a critical hit, you must finish a short or long rest before you can use it again