Level 2

• The spell's duration is 10 minutes.
• Your concentration on the spell cannot be broken by taking damage.

Level 5

• When your quarry dies, you can move the mark as part of making an attack against a creature you can see within range.
• You can apply the damage bonus on spell attacks as well as weapon attacks.

Level 9

• You gain one more use.
• The spell does not require concentration.
• When a creature under your control attacks a marked creature, it can also apply the bonus damage once per turn.

Level 13

• The damage increases to 2d6.
• You are no longer required to see a creature to target it with this spell or to switch the mark to it, provided you know its location, and the range increases to 600 feet.
• You always know the location of a marked creature provided it is on the same plane as you, and you can see it through illusion magic like invisibility.

Level 17

Favored Enemy

Choose one category: Beasts, Fey and Plants; Dragons and Monstrosities; Constructs, Elementals, Giants and Oozes; Aberrations, Fiends and Undead.

When you make an ability check relating to one of those creature types, you are considered proficient in the check, and if you were already proficient, your Proficiency Bonus is doubled. For example, tracking or grappling them, recalling information about them, or discerning their motives. Humanoids are excluded entirely; you are not an assassin.

You also learn one language associated with the creatures (respectively: Sylvan, Draconic, Primordial, Infernal).

This improves when you reach certain levels in this class:

• Level 6: Select an additional category, and you can change one of these choices whenever you finish a long rest (you do not change languages).
• Level 14: If you make a saving throw in response to a favored enemy, you are considered proficient in the save, and if you were already proficient, your Proficiency Bonus is doubled.
• Level 20: If you make an attack roll against a favored enemy, you are considered proficient in the weapon, and if you were already proficient, your Proficiency Bonus is doubled.

Natural Explorer

Choose one common type of favored terrain: Forest, hill, plain, water. And one rare: Arctic, desert, swamp, underground. At level 6, 10 and 14 in this class, you select one additional common and rare type.

You have advantage on ability checks and saving throws relating to the chosen terrain types. For example, climbing vines in the forest (Athletics check), persevering in the icy north (Constitution save), or spouting lore about undersea biology (Nature check).

You might benefit from a relevant terrain regardless of the surrounding area, like water terrain helping cross a river in a forest. Urban areas are outside your field of work entirely (including constructed areas even if they're in a forest or cave), and extreme or magical terrain is excluded but could be learned in specific circumstances (e.g. if you brave the elemental chaos' fire sea, you might add that as a terrain).