How deadly was the Mongol invasion of Europe?

According to this Venn diagram at least 27 on the mortality scale.

What measurement would you like me to use? Suppose I say, 'The invasion was exactly 78.3338749% deadly', would that help you?

From my understanding the Mongols were virtually unstoppable. They had a bow which I think was made of layers of bone which was small yet very powerful and they were experts at firing arrows on the gallop from the back of their horses. They used fast cavalry tactics unseen in Europe which the Europeans found hard to beat. They also wore silk shirts which did not pierce from arrow strike and it entered the wound with the arrow head and made it easier to pull arrows out of themselves without leaving the arrow head in the wound to infect the wound increasing their chance of survival.

The Mongols were fierce warriors and they had conquered huge amounts of territory including eastern Europe. The Mongols committed genocide along the way killing many people for the sake of killing them. Likely this caused many to avoid them if possible and spread fear which gave the Mongols an advantage. There is some speculation that it all came to an end when Europe had 3 very wet cold winters which left the ground boggy, totally unsuitable for cavalry tactics which require solid ground. Others say it was a fight over power in the conquered lands that caused the Mongols to leave Europe.

For those killed, quite deadly.

For the majority of people in Europe, not so much.

Extremely deadly for anyone who died.

it put a slant to how Europe views them

It was not very much

it sounds pretty deadly