Arcane Faliure?

[Jackfrost]

It is reasonable to think that such a thing exists but I never understood how to put it into play.

A character in my game is a sorcerer and he has +2 lether armor on and a staff in his off hand. I tried to apply some faliure but never knew how much to apply, and even so I wouldn't understand how to use the faliure

 

[Madfox]

Percentages on the chance of failing to cast a spell are given in table 5-7 on page 105 of the PHB. The chance of failure is 10% for leather armour. In my campaigns we usually roll a d20 next to casting the spells, unless we forget, which happens more often then not...

 

[Crothian]

It's real simple. Use the percentage listed in the chart. If you roll this or less then the spells fails. Subtract it from memory, and move on to the next initative number.