Lizard folk

Only a fool looks at the lizardfolk and sees nothing more than scaly humanoids. Their physical shape notwithstanding, lizardfolk have more in common with iguanas or dragons than they do with humans, dwarves, or elves. Lizardfolk possess an alien and inscrutable mindset, their desires and thoughts driven by a different set of basic principles than those of warm-blooded creatures. Their dismal swamp homes might lie hundreds of miles from the nearest human settlement, but the gap between their way of thinking and that of the smooth-skins is far greater.
Despite their alien outlook, some lizardfolk make an effort to understand and, in their own manner, befriend people of other races. Such lizardfolk make faithful and skilled allies.

Alien Minds

The lizardfolk’s reptilian nature comes through not only in their appearance, but also in how they think and act. Lizardfolk experience a more limited emotional life than other humanoids. Like most reptiles, their feelings largely revolve around fear, aggression, and pleasure.
Lizardfolk experience most feelings as detached descriptions of creatures and situations. For example, humans confronted by an angry troll experience fear on a basic level. Their limbs shake, their thinking becomes panicked and jumbled, and they react by instinct. The emotion of fear takes hold and controls their actions. In contrast, lizardfolk see emotions as traits assigned to other creatures, objects, and situations. A lizardfolk doesn’t think, “I’m scared.” Instead, aggressive, stronger creatures register to the lizardfolk as fearsome beings to be avoided if possible. If such creatures attack, lizardfolk flee, fighting only if cornered. Lizardfolk aren’t scared of a troll; instead, they understand that a troll is a fearsome, dangerous creature and react accordingly.
Lizardfolk never become angry in the way others do, but they act with aggression toward creatures that they could defeat in a fight and that can’t be dealt with in some other manner. They are aggressive toward prey they want to eat, creatures that want to harm them, and so on.
Pleasurable people and things make life easier for lizardfolk. Pleasurable things should be preserved and protected, sometimes at the cost of the lizardfolk’s own safety. The most pleasurable creatures and things are ones that allow lizardfolk to assess more situations as benign rather than fearsome.

Cold and Calculating

Most humanoids describe cold-blooded people as lacking in emotion and empathy. The same label serves as an apt depiction of lizardfolk.
Lacking any internal emotional reactions, lizardfolk behave in a distant manner. They don’t mourn fallen comrades or rage against their enemies. They simply observe and react as a situation warrants.
Lizardfolk lack meaningful emotional ties to the past. They assess situations based on their current and future utility and importance. Nowhere does this come through as strongly as when lizardfolk deal with the dead. To a lizardfolk, a comrade who dies becomes a potential source of food. That companion might have once been a warrior or hunter, but now the body is just freshly killed meat.
A lizardfolk who lives among other humanoids can, over time, learn to respect other creatures’ emotions. The lizardfolk doesn’t share those feelings, but instead assesses them in the same clinical manner. Yes, the fallen dwarf might be most useful as a meal, but hacking the body into steaks provokes aggression in the other humanoids and makes them less helpful in battle.

Utility and Survival

The lizardfolk mindset might seem unnecessarily cruel, but it helps them survive in a hostile environment. The swamps they inhabit are filled with a staggering variety of threats. Lizardfolk focus on survival above all, without sentiment.
Lizardfolk assess everyone and everything in terms of utility. Art and beauty have little meaning for them. A sharp sword serves a useful and good purpose, while a dull sword is a dead weight without a whetstone.
Lizardfolk see little need to plan more than a season or so into the future. This approach allows them to maintain their current level of influence in the world, but it limits their growth. Lizardfolk have no interest in developing writing, making long-term plans, or cultivating other methods to progress beyond their simple existence as hunters and gatherers.

Hapless Soft Ones

At their core, lizardfolk view other humanoids with an indifference verging on pity. Born into the world lacking stout scales and sharp teeth, it’s a wonder they have managed to survive for so long. The typical human would barely make it through a day in the swamps.
Still, if other creatures prove useful to lizardfolk, those creatures can trigger a protective response made all the stronger by their apparent weakness. The lizardfolk assess such beings as hatchlings, young ones incapable of protecting themselves but who might prove useful in the future if they receive care.

-description courtesy D&D Sourcebooks/D&D Beyond