Larian Studios Forums Baldur's Gate III Baldur's Gate III - Technical & Gameplay Problems Apparently I don't understand how criticals work, or d20 D&D games

The link just says "service unavailable".

The by far most likely reason for four crits in a row is that the target is stunned and was attacked from within 5 ft / 2 m.

Otherwise the chance for four critical hits is 1/20*1/20*1/20*1/20 = 1/160,000, in words once every 160,000 tries.

There are ways to force a single critical hit, and there are ways to increase the chance to critical hit, but obviously opponents in the game will not stack such effects and will never have better than crits on a 19 or 20, and even that rarely. After that there is having the advantage to almost double this range in practice, which means there is a 1/5 chance to critical hit, so then its down to 1/5 ^ 4 = 1/625 chance (the actual value is even a bit lower because the true chance is less than 1/5).

So really the stun is by far the most likely reason.