From Wiki of Worlds Unknown
If you roll a natural 1 on your first attack roll of a round, you must succeed at a DC 15 Reflex save or fumble.
- 'Named' creatures cannot fumble more than once during a given encounter, and further 1s are simply misses.
- Local Games
- On a fumble, you must draw a card from the Critical Fumble deck. Otherwise, you are subject to an attack of opportunity from your target.
- PbP Games
- On a fumble, you will typically provoke an attack of opportunity from your intended target unless the action causing the fumble might be better represented by falling prone or some other similar mishap.