How to Harvest
...

The act of removing useful body parts from a creature is referred to as harvesting . Anything that can be harvested from a creature is referred to as a harvesting material or simply material. In general, only creatures that have died may be harvested, but there may be some exceptions based on context.

This section details the steps associated with actually performing a harvest, and any factors that may influence it.

Appraising
...

My mother always used to press the importance of taking one’s time and not jumping into things. This advice holds true whether one is harvesting a creature, engaging in a fight, or literally jumping into a river.” – Hamund

Before a player begins hacking and butchering their hunt, they may instead choose to take a moment first and appraise the creature to be harvested. To do this, they must spend 1 minute examining the creature to be harvested and then roll an Intelligence check, adding their proficiency bonus if they are proficient in the skill corresponding to that creature (see table below). For example, appraising a Beholder (which is an aberrant), the check would be an Intelligence (Arcana) check, while appraising an Ogre (which is a giant) would require an Intelligence (Medicine) check.

The DC of the check is equal to 8 + the Harvested Creature’s CR (treating any CR less than 1 as 0). Success on this check grants the player full knowledge of any useful harvesting materials on the creature, the DC requirement to harvest those materials, any special requirements to harvest them, and any potential risks in doing so. In addition, any harvesting check made on that creature by that player is rolled at advantage. A character may only attempt one appraisal check per creature.

Monster Type/Skill Check
...

Monster Type Skill
Aberation Arcana
Beast Nature
Celestial Arcana
Construct Investigation
Dragon Nature
Elemental Arcana
Fey Arcana
Fiend Arcana
Giant Medicine
Humanoid Medicine
Monstrosity Nature
Ooze Investigation
Plant Nature
Undead Arcana

Splitting up the Responsibilities
...

Some party members may prefer to let one character handle the appraisal of materials, while another more dexterous character handles the actual harvesting. In this scenario, all benefits of appraising a creature are conferred to the player doing the harvesting, so long as the player that performed the appraising assists the harvesting player through the whole duration of the harvest.

Harvesting
...

In order to harvest a creature, a character must make a Dexterity ability check using the same skill proficiency as listed in the above appraising table. For example, a character attempting a harvest check on an Aberrant would receive a bonus equal to their Dexterity modifier and their proficiency in Arcana (if they have any).

This check reflects a character’s ability to not only properly remove the intended item without damaging it, it also involves any ancillary requirements of the harvest such as proper preservation and storage techniques

Each individual item in a creature’s harvesting table is listed with a DC next to it. Any roll that a player makes that equals or exceeds this DC grants that player that item. Rewards are cumulative, and a player receives every item with a DC equal to or below their ability check result. For example, rolling a total of 15 on a check to harvest an Hamund's Harvesting/Harvest Table A/Azer will reward the player with both “azer ash’, and “azer bronze skin”, but not a “spark of creation”. If they so wish, players may opt to not harvest a material even if they have met the DC threshold to harvest it.

Only one harvesting attempt may be made on a creature. Failure to meet a certain item’s DC threshold assumes that the item was made unsalvageable due to the harvester’s incompetence.

For most creatures, the time it takes to harvest a material is counted in minutes and is equal to the DC of that material divided by 5. For huge creatures however, it is equal in DC of that material, while for gargantuan creatures, it is equal to the DC of that material multiplied by 2.

Particularly Violent Deaths
...

"I know that it is a dangerous world out there, and we all must do what we can to survive. But do understand that there are few people out there that are in the market for a charred owlbear pelt with more holes in it than the plot of a bad novel." - Hamund

This guide assumes that most creatures you attempt to harvest died in direct combat and thus already accounts for the idea that you are harvesting creatures that are not in pristine condition. However, some deaths are more violent than others and can make harvesting useful materials either extremely difficult or downright impossible. Such examples include burning by fire, dissolving from acid, or being completely crushed under a pillar of stone. In these cases, raise the DC for harvesting any of that creature’s materials by 5. Alternatively, the DM may decide that well orchestrated hunts result in a carcass that is prime for harvesting, such as creatures killed mostly through psychic damage, or those killed in one clean attack. In these cases, the DM should lower the DC for harvesting any of that creature’s materials by 5

Furthermore, the DM may adjudicate whether or not some of a creature’s individual materials have been made useless due to effects imposed by them in the course of their death. Examples may include blood being tainted from poisoning, or their pelt being worthless due to excessive slashing/piercing damage.