How exactly do item drops work?

Hey, I'm doing some hobby code & i'm trying to replicate the PSO drop system for funsies.

While digging around the code & other forum guides I've been piecing together the item drop algorithm.

So from what I can tell...

1. Every monster has a drop % for them to drop *any item at all*
This appears to be fixed to the monster data.

2. If it is decided that an item will be dropped, the next roll will determine if its a common or a rare.

Common Branch -

C1. It will decide what type of common it is.

C2. If it is an "armor" then it will decide if it actually an Armor, a Shields or a Units

C3. It will then generate the attributes of the item.

Rare branch -

R1. It will decide which rare is dropped based on map, difficulty & section id.

R2. It will generate the attributes of the rare.

Can anyone tell me if this is correct?

Extra Questions...

1. I can't understand what drop rate increases. E.g. if ephinea is running at 130%, does that mean that monster drop % ger bumped...or the % that an item will be a rare rather than a common.

2. In C2, is the decision for Armor / Shield / Unit determined by chance or by the monster type. I've seen differing data during my digging.


Staff member
Your branching is mostly correct, yes. However, in the common branch path, when the server decides to drop equipment, the ItemPT already lets us know whether to drop a weapon, armor, shield or unit for that monster. So that isn't random at all.

Also, what Ephinea's drop rate boost actually boosts is pretty clear. As the % it's increasing is shown when you join a game and checked via /partyinfo. It clearly states Rare Drop Rate. So, it's just the chance the item dropped is a rare item. The drop anything rate does not get boosted.
Thanks Sodaboy, I think I've just got it.

So does every monster have a defined rare that it can drop, and *only* that rare? So for example when a drop table says it has a 1/7463 chance...thats the chance that the common drop will be upgraded to the defined rare?

How easy is it to look at the data inside the ItemPT?


Someone else asked me about the data on itemPT, here is a pic of something I was doing
The data (most of it) is pretty straight forward, just look at the PT struct in the ship source.

From the old source (again xD) ... a monster has just 1 rare, iirc Soda did on the drop table a dar + rare rate right? ... in that case the rate there is your chance of getting the rare (common drop upgrade included).


Nah, it's not finished... A while ago, I saw a picture of the same thing (on Eden) which was Doberman who was making it, but I didn't see links anywhere, no idea if he ever finished it/released it.