The Divide By spells duplicates the next spell into a number of copies – 2, 3, 4, or 10 – while reducing their damage dealt.
They will only reduce projectile damage. All other damage types apply as normal.
They don't quite behave like a spell in itself in every situation, and it applies cast delay like a modifier (even though it's technically not that either).
The first 3 Divide By spells (2, 3, 4) are unlocked by opening the Coral Chest, while the Divide By 10 is unlocked by bringing the Curse of Greed to the Avarice Diamond in The Tower.
How it Works
Please note that this page is highly incomplete and does not adequately explain these spells. They are very complicated. This is still a good introduction to the function of Divides, but for a far more comprehensive and detailed understanding of them, check out the Expert Guide: Divide By Spells.
Here are the basics:
When applied directly to projectiles, it acts similarly to a multicast array containing the duplicated spell (with reduced damage).
Is the same casting order as:
This works with modifiers and after triggers as well, so:
Is mechanically equal to:
Those multicasts are never actually created though, they're just there to illustrate behavior. In actuality, the original spell is deleted and new spells (with reduced damage output) are created in their place and cast at the same time.
When Divide By # is applied to a modifier, the spell works a bit more strangely.
Becomes equivalent to this in the first cast:
The divide by effectively creates 2 additional copies of the Damage Plus. The first copy is prevented from drawing additional spells, but the second copy is able to draw into the real Damage Plus and Spark Bolt, which means you get a total of 3 Damage Pluses.
The next cast from that wand will be equivalent to:
This is because after the Divide By finishes copying the second Damage Plus (which drew the real damage plus and spark bolt), it will discard the next spell, which is the bouncing burst. The bubble spark gets cast, which then wraps into the bouncing burst.
It's the same for multicasts.
Is equivalent to:
As in the previous example, the first Triple Scatter Spell is unable to draw, but the next two are. Which means that you get an effective 5 multicast, the same as 2 Triple Spells. The spread from all three Triple Scatter Spells will be applied.
Each Divide By spell has an iteration limit. Divide By 2 has a limit of 4, Divide By 3 and 4 have a limit of 3, and Divide By 10 has a limit of 2. Once this iteration limit is exceeded, chaining more Divide By spells will have no effect.
Will cast 100 Spark Bolts as expected, since the first Divide By will cast the second Divide By 10 times.
Will still only cast 100 Sparks Bolts, since the third Divide By 10 exceeds the iteration limit of 2.
The iteration counter is shared for all Divide By spells so this:
Will cast 20 Spark Bolts, while this:
Will cast 200 spark bolts.
Things becomes more complicated when Divide By spells are placed after a multicast.
In this example:
The multicast will draw these four blocks, in order:
Notice how the second casting block begins with the spells following the first block, but is followed by the Divide By's and Spark Bolt. Each following block wraps into the same chain, except one spell further on the chain of Divide By's. A chain of n divide by spells needs a n+1 multicast in order to cast all possible blocks. Each of these blocks will have its own iteration counter.
Here is a list of common ways to divide spells efficiently. Read the Expert Guide: Divide By Spells for a better understanding of how these work.
Divide by 800 on a spell without draw (e.g. a projectile)
This casts 800 copies of a Spark Bolt, which is the largest possible purely using Divides.
Divide by 800 on a spell with draw (e.g. a modifier)
This casts 800 copies of the Critical on Wet. In order to properly divide the modifier, the Divide By chain is draw canceled, which means that you need the additional draw from the Double Spell to cast anything after.
Divide by 800 add trigger
These examples cast 801 copies of both Critical on Wet and Homing. The first build works because the Blood Magic is a utility spell without a related projectile, which causes the Add Trigger to fail (which is good since Add Trigger would normally ruin the deck for the next copy), but only after casting copies of the modifiers. In the second build, Add Trigger fails because it reaches the end of the wand with nothing to apply to. Add Timer and Add Expiration Trigger have the same behavior here. The Blood Magic can be replaced with Blood To Power, Gold To Power, or a projectile/static projectile with 0 charges (e.g. 0 charge Healing Bolt).
Divide by 800 spell duplication
This gives 800 additional copies of Critical on Wet, Homing, and Spark Bolt. The Alpha calling Tau is used to hit the recursion limit, which prevents Spell Duplication from copying a Divide By or greek letter and ruining the deck before all 800 copies complete. It is also possible to use Gamma with Tau at end of the wand, with an additional double cast at the beginning, instead of using Alpha.
- The virtual copies do not need extra free spell slots in the wand to function, so can be used to make even low capacity wands fire many more spells than normal.
- Divide By spells have a hidden explosion radius reduction, -5 for div2, -10 for div3, -20 for div4, and -40 for div10.
- Each Divide By spell sets the pattern angle to 5, which is the variable that formation spells use. A pattern angle of 5 means that projectiles will be distributed evenly along a 10 degree arc centered where you're aiming. Only the last pattern angle set is used, so a Divide By following a hexagon formation will have 5 pattern degrees instead of 180.