Infernal ashes

Infernal ashes are a 100% drop from black demons, abyssal demons, tormented demons, nechryaels, and most demon bosses. They can be scattered for 62.5 Prayer experience, taken to the Ectofuntus for 250 Prayer experience or used at a POH gilded altar with both incense burners lit for 218.7 Prayer experience. Note that if you use demon ashes on the Ectofuntus, you do not need to use them on the bone grinder to produce bonemeal.

They can also be used when killing the demons mentioned above to fill an infernal urn. It takes 25 infernal ashes to fill an infernal urn, which grants 1,875 experience when teleported (equivalent to 75 experience per infernal ashes, which is an extra 20%).

These ashes are usually a cheaper alternative to dragon bones, although prices often fluctuate, and players should look into the experience-cost ratio of each before any major training.

Common collection methods
Players can "camp" in the Morytania Slayer Tower to kill abyssal demons. This method is very similar to camping at green dragons, because both are 100% drops. Using any beast of burden familiar gives you a great advantage, allowing you to carry more infernal ashes to the bank. With 96 summoning, players can summon a pack yak and use their winter storage scrolls to send ashes directly to the bank, minimising bank trips. Currently, the price for infernal ashes is  coins, so this method can be used for money making or to gain prayer experience.

This method has the ability to make between 400,000 - 750,000 per hour, not including Abyssal whip, Abyssal wand, and Abyssal orb drops. The minimum is around 400,000 per hour, which requires killing 3 abyssal demons every minute (this is relatively easy for higher levelled players).

Alternately, nechryaels can be killed instead if you lack the 85 Slayer requirement. As with abyssal demons, they have infernal ashes as a 100% drop and are situated nearby the demons in the Tower.

Many higher levels tend to leave infernal ashes on the ground while training Slayer on abyssal demons or nechryaels. Lower levelled players who cannot kill these monsters themselves can take advantage of this, as they can pick up these ashes and bank them in nearby Canifis. This collection method is made faster if the player has completed Desert Treasure and has 50 Construction, allowing them to have a portal chamber with Kharyll Teleport.

Another good way to collect infernal ashes is to kill black demons in the Taverley dungeon. With this method you can either take high level defensive armour with good food and/or a bunyip, or you may take armour with high prayer bonus to use protect from melee or deflect melee continuously. It is recommended to have 70 Agility (for the pipe shortcut) or 80 Agility (for the spike trap shortcut), and a teleport to leave the area. Black demons also have decent drops, which makes this method very profitable for people who do not have 85 Slayer for abyssal demons.

For those who have completed the Underground Pass quest, these ashes can be gained from comparatively low level demons, specifically Doomion, Othanian, and Holthion, the level 112 demons that guarded Iban's shadow during the quest. The main drawback is it can be a hassle to get there, as you need a bow, at least one arrow, a spade, a rope, and a lot of energy just to get back to them if you have yet to unlock Tirannwn. However, for those who have, entering through the well of voyage lands you in the area with these demons. Due to the remoteness of the location and distance from a bank, this is not a good way to collect ashes if you want to sell them or use them at POH altars or the Ectofuntus. However, all three are easily ranged or maged, and if you are more interested in gaining prayer experience through the use of urns or by scattering the ashes you could gain a lot of experience in a short amount of time. For those who prefer melee, Kamen is still available for food as he was during the quest, if you're willing to pay or can stomach his brew.

A fast, but expensive, way to collect infernal ashes is to use chinchompas or burst or barrage spells on any appropriate demon that gathers in large enough numbers, such as nechryael in the chaos tunnels or slayer tower. This method is risky if using the chaos tunnels, however, due to PKers in the short journey through the wilderness to the tunnels, but this can be avoided using the Dagon'hai route.

Trivia

 * Before 25 February 2011 one could un-note infernal ashes using a butler at a POH. Jagex has since changed this, now they can no longer be un-noted by any butler.
 * On the first day of release, the Grand Exchange price for infernal ashes was set at 1,700 coins. However the ashes were actually selling for over 5,000 coins, which was closer to the price of bones giving similar prayer experience.
 * A player choosing to use infernal ashes all the way from 1-99 Prayer, using a gilded altar with lit burners and no other experience boosts, would, if all the ashes were bought at the current medium price on the Grand Exchange, spend.
 * Additionally the first two ashes would take them straight to level 5 Prayer.
 * Using the Ectofuntus would cost . Simply scattering the ashes would cost.

Infernal ashes