Question

What happens if I kill a Lion Knight ? If I understand it right, they give no loot and are "friendly" to players.

Answer 1

These Lion members are loyal to their current leader and peaceful. They do not attack players. There is no reason to kill them since they yield no experience nor loot. They are not even listed in bestiary.

Lion Archer, Lion Knight, Lion Warlock, Lion Commander

Note, however, that if you kill one of the Lions you'll be sent to jail for a few seconds.

Source: https://tibia.fandom.com/wiki/Order_of_the_Lion & https://tibia.fandom.com/wiki/The_Order_of_the_Lion_Quest/Spoiler