Identifying a Creature. Knowing what specie or type of creature you face – its hit points, traits, abilities, attack options – is valuable in combat. The rules don't expressly address creature identification. Here is a house rule.
1. Should an ability check be required? The GM could simply rule that the character has knowledge of the creature or, alternatively, that there is no chance of this, based on the following:
The more common the creature, the more likely it has been confronted before.
The higher the character level, the greater the variety of creatures previously encountered.
2. If the GM believes that there is a chance you know something meaningful about the creature, the GM could require an ability check linked to the creature type in question. See the table.
3. The GM could consider whether the character's background, race, languages known, or class (see the table) are such that the character can identify the creature or, alternatively, that any required ability check can be made with advantage.