Countering FX
From D20advanced
In some circumstances one FX may counter another, negating it. Generally for two FX to counter each other they must have opposed descriptors. For example, light and darkness FX can counter each other as can heat and cold, water and fire, and so forth. In some cases FX of the same descriptor can also counter each other. The GM is the final arbiter as to whether or not an FX of a particular descriptor can counter another. The Nullify FX can counter any FX of a particular descriptor (or even any FX at all) depending on how it is configured.
How Countering Works
To counter an FX, take a ready action. In doing so, you wait to complete your action until your opponent tries to use an FX. You may still move or take another action, since ready is only one action.
You must be able to use the countering FX as one or fewer actions to ready it. FX usable as a reaction do not require a ready action; you can use them to counter at any time. FX requiring two actions or longer cannot counter another FX in combat, although they may potentially counter ongoing FX.
If an opponent attempts to use an FX you are able to counter, use your countering FX as your readied action. You and the opposing character make FX checks (d20 + FX rank). If you win, your two FX cancel each other out and there is no FX from either. If the opposing character wins, your attempt to counter is unsuccessful. The opposing FX works normally.
Countering Ongoing FX
You can also counter a maintained or lasting FX, or the lingering results of an instant FX (like flames ignited by fiery Damage). This requires a normal use of the countering FX and an opposed FX check, as above. If you are successful, you negate the FX (although the opposing character can attempt to re-establish it normally).
If countering a lingering FX no longer under the user’s control, the countering character makes an FX check as usual, but the Difficulty is simply 10 plus the rank or bonus of the FX, since there’s no real opposition.
Instant Countering
You can spend a hero die to counter another FX as a reaction using an FX that normally requires one or fewer actions without the need to ready an action to do so.
