https://rentry.org/ragnav
Ragna/v/3 - x3-x10 Pre-Renewal with a lot of renewal-flavored customization
Ragnadev's server for the 4chan community

>Basic resources:
>Database
ratemyserver.net
www.divine-pride.net - has some of the non-English and kRO items
>Wiki
iRO wiki has a lot of information, but keep in mind its supposed to be a wiki for iRO
irowiki.org - /wiki/ for renewal, /classic/ for pre-pre
>Skill descriptions
Over the several iterations of the game, skill descriptions vary wildly. There's also the issue of skills behaving differently depending on the emulator. iROwiki is mostly complete but sometimes it's completely wrong, specially the pre-re version since those are no longer open for editing.
Pre-Renewal:
github.com/llchrisll/ROenglishRE/blob/master/Addons/Revised%20%Pre-Re%20%SkillInfoz/data/luafiles514/lua files/skillinfoz/skilldescript.lub
Renewal:
irowiki/wiki/ probably still best but scroll down to changelog. Since iRO added 4th jobs, it's now showing the new descriptions for skills. Some 3rd job skills were entirely reworked.
>Calcs
rocalc.com
skillsim.irowiki.org
>Source code:
github.com/rathena/rathena
github.com/HerculesWS/Hercules
If you want to look up a skills formula, buff effect or anything hard coded, it's all inside src/map/ folder. battle for damage, skill for skill conditions, script_constant for variables. Sometimes pc file has useful stuff too.
>Other
github.com/llchrisll/ROenglishRE - RO translation project

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