The Night Shade of Greyhawk and the Hallowed Revenant Amphoras
Critical Success and Failure
A critical success for an attack roll is an automatic hit, with the exception for powers or feats that can intercept a hit (stated before the attack roll). In addition, critical successes cause double the damage rolled for the attack. In the case of attacks that cause duration effects, the damage is doubled for the entire duration (example – throwing a poisoned dart hit the target in a vital artery causing the poison to do more damage) with saves allowed as normal.
A critical failure for an attack roll is an automatic miss, regardless of powers or feats. An attack roll is then made against the attacker's AC to see if they hit themselves. If the attack hits, normal damage is taken by the attacker. Duration is normal as well for duration effects, with saves allowed as normal.
A critical success for a skill check indicates a success at any DC level. The successor then gets all benefits of a full success and potentially an extra tid bit of information or leverage.
A critical failure for a skill check is an automatic failure, with potentially dangerous misinformation or irrational lack of attention.