Every fight and every criminal action in Shadowrealm resolves on the server from your character's eight stats, the gear you are wearing, and whatever buffs are running. Nothing about the outcome is decided on your device, which is why the numbers below are worth understanding: they are the whole model, and they are the same numbers the server uses.
Attack, Defense, Speed, Luck, Stamina, Magic Power, Critical Strike and Dodge. Every point comes from one of three places: your base character, the gear you have equipped, or a temporary buff. Gear and buffs are additive with your base, so a "derived" stat is simply the sum, and that sum is what fights and actions read.
Criminal actions do not simply succeed or fail on a whim. Each action has a base chance, your stats move it, and the result is then clamped: never below 5% and never above 95%. Both ends of that clamp matter. The floor means no action is ever truly hopeless, so a low-rank character attempting something ambitious still has a real chance. The ceiling means no amount of stacking ever makes an action free: there is always risk, and a fully geared character still fails roughly one attempt in twenty.
Luck is the most efficient stat to raise for this purpose, at 0.5% per point, and it is doing double duty because the same points also improve what drops when you do succeed. If you are choosing where to spend, Luck is rarely the wrong answer.
A fight runs up to 20 rounds. Each round, the attacker's damage is computed from their stats, reduced by up to 50% by the defender's Defense, multiplied by 2x if it crits, and cancelled entirely if the defender dodges. A small random jitter of about 15% down to 15% up is applied so two identical characters do not produce identical fights, and damage never lands below a floor of 1, so a heavily armoured opponent can still be worn down rather than becoming literally invulnerable.
Player-versus-player fights use a separate, larger health pool: 10x your normal maximum. That is deliberate. It makes a duel a contest of sustained output rather than a coin-flip on who lands the first critical hit, and it means Speed and Defense earn their keep over the course of a fight instead of being decided in one exchange.
Gear has condition, from 1,000 down to zero, and it degrades as you take damage: roughly 0.1 points of condition per point of health lost. This is the most commonly missed mechanic in the game, because nothing stops you fighting with ruined equipment. It just quietly performs worse.
The penalty is stepped, not smooth. Between 25% and 50% condition your gear's stats count for 90% of their value; below 25% they count for only 80%. A full set of legendary equipment at 20% condition is meaningfully weaker than a mid-tier set in good repair, and the character sheet will not shout about it. Repair at a Blacksmith before a serious fight, not after losing one.