Prior to becoming an adventurer, your path in life was crystallised by one dark moment, a loss or tragedy perpetrated by a monster or monsters that lit an inferno of hatred in your soul. Now you are propelled onward by this flame of hatred, none shall escape your wrath, you will bring ruin down upon every member of your chosen prey that you can find. Choose one monster type to become your designated prey and choose what they did to you to incur your hate.

Those who look deep into your eyes can see the fury that burns within your heart, ordinary people are incapable of lying to or misdirecting you if you specifically question them about your chosen prey, what information they have they will give fully and completely to the best of their ability, not wishing to incur your wrath. You have a comprehensive and detailed knowledge of your chosen prey's characteristics and gain Advantage on any checks relating to their behaviours, capabilities or motivations, you also cannot be surprised by any combat involving your chosen prey. 

However your hate is very strong and if presented with the chance to avoid Slaying your prey, e.g. sneak past a group of your chosen prey instead of attacking, you must make a DC=15 Wisdom Saving Throw to successfully suppress your hate and avoid Slaying them. Every successful save increases the DC by 3 while every successful combat in which you personally Slay at least one member of your chosen prey reduces the DC by 2 to a minimum of a DC=5, The DC resets to a DC=15 after a downtime of one week or more. You do not need to roll if planning an action that will lead to Slaying your chosen prey, e.g. sneaking past a group of your chosen prey in order to set up a later ambush for them.