Question

What creatures occurrence is common?

Related with the Find Fiend spell/creatures.

Answer 1

Most of creatures, which you can meet in Tibia in noticable amount you can consider as "common", but to be sure what type of creature is each of them - simply check it in the bestiary.

The more blue diamonds you can see next to the creature, te more rare it is. Common creatures got only one diamond.

Answer 2

Common Creatures have been listed on Tibia Wiki (the list contains at the moment 526 monsters and will not fit into answer) :

https://tibia.fandom.com/wiki/Category:Bestiary_Common_Creatures

Common creatures are the creatures with regular spawn type, which are not triggered by specific mechanics nor spawn only during the raid. They will be marked with one diamond in your Bestiary.