Following the Xenobiologist archetype means that you are on the forefront of scientific exploration when it comes to alien flora and fauna. As a Xenobiologist you exemplify what it means to be an explorer, but you also are often what stands between your team and the wilds of alien worlds. 

Xenobiologist Tech (magic)

Starting at 3rd level, you learn an additional spell when you reach certain levels in this class, as shown in the Xenobiologist Spells listed below. The spell counts as a ranger spell for you, but it doesn’t count against the number of ranger spells you know. 

• 3rd level - Alarm
• 5th level - Locate Animals or Plants
• 9th level - Conjure Animals
• 13th level - Faithful Hound
• 17th level - Commune with Nature 

Inquisitive Spirit

At 3rd level, you gain the ability to ascertain the attributes, strengths, and weaknesses of animals and plants. As a bonus action you can make an Intelligence (nature) check on a beast or plant you can see, contested by the target’s Dexterity (stealth) check. If you succeed you learn the target’s immunities, resistances, and vulnerabilities to damage. If the target is a beast or sentient plant, you also have advantage on Wisdom (animal handling) checks against the target.

This benefit lasts for one minute or until you successfully use this feature on a different target. 

Scientific Tactics

At 7th level you gain one of the following features of your choice. 

Analysis and Research

At the end of combat you can use an action to roll hit dice. You roll a number of hit dice equal to the number of rounds the conflict lasted. You regain a number of hit points equal to the number rolled plus your level in the ranger class. 

Keen Observation

You have advantage on saving throws against dangers you can see.

Tested Hypothesis

When a creature hits you with an attack, you can roll a Wisdom (insight) check against a DC equal to 10 or half the damage taken, whichever is higher. On a success, you gain a +5 bonus to AC on all subsequent attacks from that creature for the rest of the turn. If the creature which triggers this feature is a beast or plant you have advantage on the Wisdom (insight) check. 

Applied Xenotoxin

At 11th level you gain ability to turn your studies of natural toxins and alien life to your advantage in combat. All attacks made by you deal an extra 1d8 poison damage. When dealing this poison damage you can force the target to make a Constitution saving throw against your spell save DC. On a failure the target is paralyzed for 1 minute. The target may repeat the saving throw at the end of its turn to end the effect early. 

You can trigger the saving throw up to a number of times equal to your proficiency bonus. 

Xeno-Unity

At 15th level you have become so in tune with alien life that you can read the movement of flora and fauna perfectly. Mimicking the fighting style of some of the most ferocious animals you can lash out at your foes in new ways. When targeted by an attack you can use your reaction to make an attack against that the creature that targeted you. On a hit your strike is an automatic critical hit.

You can use this feature up to a number of times equal to your proficiency bonus.