Effects of Decadence
Depending of your decadence level, your realm can get positive and negative effects. These effects apply to demesne income and troop morale. At 25% decadence it will not have any effect. Go below that and you will get increased demesne income and troop morale. Go above 25% and you'll get decreased demesne income and troop morale. If you have above 75% decadence, you might be invaded by tribes who want to usurp your title!
 Acquiring Decadence
Adult male members of your dynasty with no or insufficient land will slowly increase your decadence. Dynasty members who are younger than 16 years old or who are female do not affect decadence, nor do prisoners or characters outside your realm (unless their liege also belongs to your dynasty). The amount of decadence gained per character increases with your rank, the total size of your realm, and the relatedness of that character to you. It is decreased by every title held by that character, with higher-ranked titles counting for more, as well as by holding councillor positions. Decadence gain is also multiplied by the size of your demesne divided by your demesne limit, so a small demesne will limit decadence growth. Decadence gained from a relative with sufficient titles can be zero, but is never negative.
Some events triggered by bad traits (Cruel, Cynical, Arbitrary etc.) will also increase your decadence.
 Managing Decadence
From the Religion tab you can see the head of your Religion (Sunni/Shi'a Caliph) along with any active Jihads called by your Caliph. Below that is a list of your unlanded or insufficiently landed dynasty members. From here you can address your decadent dynasty members in a few ways.
Land Grants - The easiest and most beneficial way to not only reduce how much decadence per month you receive, but also one of the few ways you can lower your current decadence. The higher level the title the more decadence will be removed.
Imprisonment - Another slightly more tyrannical approach is simply to purge the decadent members of your dynasty by granting them an indefinite stay in your dungeon. Since you're a Muslim you won't get tyranny for just imprisoning dynasty members. The only people who will care is their parents so make sure they aren't too powerful and/or are properly bribed.
Holy War/Jihad - Calling a Holy War and participating will usually remove large amount of decadence (50-100%) depending on your war contribution. The decadence will only be removed at the end of the war however so plan accordingly.
Crusades - Successfully repelling a crusade will also lower decadence depending on war contribution.
Ramadan - Available through your decisions window Ramadan is a great event chain to lower your decadence and can reduce decadence by 5 points.
Furusiayaa Tournament - Available through your decisions window the Furusiayaa Tournament will lower your decadence by 5 points.
Events from Good Traits - There's also a small chance to lose Decadence through various events. As previously mentioned these generally require good traits to happen.
- Decadence gained per month will also go down by a small but noticeable amount whenever you or a dynasty member participates in battles or sieges. As such you should generally make sure either your character or a dynasty member is leading the army.
- Executing dynasty members, with the exception of your own children, will not incur tyranny for Muslims. In addition you can make sure to have as many dynasty members as possible participate in battle to increase their chance of dying an early death.
- Give titles to members of your dynasty to avoid gaining Decadence
- Bad traits can increase Decadence
- The Ramadan decision is a great way to reduce Decadence
- Good traits can reduce Decadence
- Kill off as many dynasty members as possible
- Try to get 0% Decadence
- If you can't reach 0% Decadence, try to stay under 75% Decadence