How does Apollyon's starting item "Void" work?

The Void is a very powerful active item because it allows you to combine the effects of multiple active items into one super active item.

As per the wiki, when you use Void, two things happen:

1. All items on a pedestal in the current room are "consumed" (destroyed).
   • If the consumed item was a passive item, you will gain a small, random modification to one or more of your stats. This modification is usually positive, but can occasionally lower your stats as well. This modification is permanent for the rest of the run.
   • If the consumed item was an active item, the Void gains that item's effect the next time it is activated.
   • Note that the item has to be on a pedestal for it to be consumed... that means items from the shop or devil deals will not count unless they have been paid for already (or have been doubled using Diplopia).
2. Any active effects that have been consumed previously will activate.
   • Active effects DO stack. For example, if Void was previously used on Guppy's Head and Telepathy for Dummies, using the Void again will spawn some friendly blue flies and grant you homing tears for the rest of the room.
   • After the balance patch on January 5, 2017, the only exceptions to this rule are items that can only be activated once (such as Pandora's Box) - after they are consumed, they will activate one time, but never again, just like the regular item. Before this patch, single-use actives could be used multiple times, which was extremely strong.
   • If you save and quit the game, then continue the run at a later time, all active effects that you've collected so far will be gone. The Void will once again be a blank slate, just like at the start of the run. This is because the collected effects are not stored in the save file and only persist on a per-session basis. If you've collected a lot of effects, try to complete the run before quitting the game unless you're okay with losing them all.

These two effects happen in order, which means that when you consume an active item, it will be consumed and then you'll also get one activation out of it. Therefore, it is sometimes to good to use the item on its own first, then consume it. For example, using a Book of Revelations will give one soul heart, then you can use Void to consume it and gain another soul heart.