Anyone who rolls a 1 while attacking has a chance of fumbling. This works very much like the critical hit rules: rolling a 1 does not mean a fumble, but rather the threat of a fumble.

Once a fumble threat exists, the character, monster or NPC rolls another d20 attack roll. If the second roll also misses the target, then a fumble has occured. Note, it is not necessary to roll another 1 on the second roll, any miss will result in a fumble.

Fumble Effects

Roll 1d100 and compare the result to the following chart. There are results that will not apply in certain situations - for instance, someone that does not wear armor cannot get a borken armor strap, nor can you you drop a weapon when fighting unarmed. Results that cannot apply are treated as if there had been no fumble.

(Chart based on fumble table from Runequest by Steve Perrin & Friends (c) 1978 the Chaosium)

d100	Fumble	Effect
01-08	Slip	Make moderate dexterity DC (10) or fall prone
09-12	Stumble	Make difficult dexterity DC (15) or fall prone
13-15	Trip	Fall prone, no other action this turn
16-21	Off Balance	Make easy dexterity DC (5) or lose rest of round
22-28	Lose Grip on Weapon	No other action this turn
29-35	Weapon Snagged	No other action this turn and flat-footed until next round
36-42	Shield Strap Breaks	Must drop shield
43-45	Armor Strap Breaks	AC goes down by one until repaired
46-50	Entangled with Foe	Both take no other action this round
51-55	Drop Weapon	Move equivalent action to recover weapon
56-60	Weapon Knocked Away	Full round action to find and recover weapon
61-65	Weapon Shatters	Opponent hits your weapon and does max damage
66-70	Hit Self	Roll weapon damage only
71-75	Hit Self	Roll full regular damage
76-78	Hit Self	Roll full regular damage and no other action this round
79-80	Critical Hit Self	Roll full critical damage
81-85	Sheild Hooked	Shield does not help AC till end of next round
86-87	Twist Ankle	Make hard dexterity DC (20) or fall prone and half speed 10 minutes
88-90	Hit Friend	Roll full regular damage to nearest friend
91-92	Critical Hit Friend	Roll full critical damage to nearest friend
93-96	Helm Slips	All attacks at -2 until fixed (fixing is a full round action)
97-98	Helm Slips	Blind until fixed (fixing is a full round action)
99	Distracted	Flat footed until next round
00	All Bad All The Time	Roll three times on above table and apply them all