Biting

FL bites ML's neck / shoulder twice. Ep 2. Ep 11.

FL bites ML's hand in Ep 11. 

ML makes a point of biting the FL's lip during a kiss, sort of as punishment. 

SFL also gets the SML to bite her arm to drink her blood, which will ease his pain. Ep 27.

Bite marks are shown on the ML's shoulder in ep 24 after the lead's first time.

Ep 47 of 56 (20 of 29). ML and FL bite each other to create a symbolic bond.

FL bites the SML's jaw to shock him so she could push him away as the ice was breaking beneath them.

The ML saw the bite marks and bit the FL's neck out of possessiveness / jealousy and as a punishment / warning.

Ep 5

FL bites the ML's ear and arm while hallucinating.

Later, the ML gets her to bite his arm again to jog her memory. 

One male character bites the FL several times to drink her blood. 

The FL bites another male character's hand in episode 14. 

Ep 2 / 3

The full moon causes the ML severe pain. He bites the FL's lips because only a taoist's blood can relieve the pain, which is... a new one.

Ep 12

While tormented by dark energy, the FL bites her own hand. When the ML can't get her to stop, he offers his own hand for her to bite instead. After a moment of hesitation, she does bite his hand. Hard.

Ep 9 both

Ep 24/42

ML bites FL's ear while placing a curse on her to have nowhere to stay except by his side. 

Spoiler: rather than a curse, it's a sign of devotion that links their senses so the ML knows when the FL is in danger.

The FL links her life to the ML's so he cannot kill her. When one of them is wounded, the other feels it. This leads to some finger biting. 

FL bites ML's shoulder in anger. Episode 23.

Also lots of biting during actual fights.

FL bites the ML's hand. 

Ep 11.

ML bites ML's ear while drunk.

FL bites the ML's ear while drunk.

Episode 3

FL bites ML's hand that he uses to cover her mouth to keep her silent.

FL bites ML's lip hard while drunk. Says she's eating strawberries.

ML bites FL's ear while pretending that he's going to force himself on her to scare her.

Ep 8

One ML ties the other up and they fight

The FL bites the ML's arm hard. 

Second couple  - SFL bites SML for revenge

Ring bites