What is the default Seljuk Invasion game rule in CK3?

Default: The Seljuks will invade some time after the year 945. (patch 1.20.1.2)

Does changing the Seljuk Invasion rule disable achievements?

Yes for “Never”: the file gives it the flag blocks_achievements. The other settings keep achievements on.

Game rule · Difficulty · Historicity

Seljuk Invasion

Legacy of Persia (by the code in its key)

Default
Never ✕
Random

Seljuk Invasion is a game rule in Crusader Kings III (Difficulty and Historicity) with 3 settings: Default (the default), Never and Random. “Never” disables achievements. Patch 1.20.1.2, from game/common/game_rules/00_game_rules.txt.

This section as JSON: /raw/game-rules.json

Quick answers (2)

What is the default Seljuk Invasion game rule in CK3?: Default: The Seljuks will invade some time after the year 945. (patch 1.20.1.2)
Does changing the Seljuk Invasion rule disable achievements?: Yes for “Never”: the file gives it the flag blocks_achievements. The other settings keep achievements on.

3 settings

Default
Default
The Seljuks will invade some time after the year 945.
default_seljuk_invasion
Never
Disables achievements
The Seljuks will not invade.
The script checks it once, in 1 place
On actions (the game's own hooks) 1
- yearly_global_pulse
Every has_game_rule = never_seljuk_invasion in game/common and game/events, by the top-level object it sits in.
never_seljuk_invasion
Random
The Seljuks will invade at a random date.
The script checks it once, in 1 place
On actions (the game's own hooks) 1
- yearly_global_pulse
Every has_game_rule = random_seljuk_invasion in game/common and game/events, by the top-level object it sits in.
random_seljuk_invasion

Source: game/common/game_rules/00_game_rules.txt line 1209 (key dlc_fp3_seljuk_invasion), modifiers from game/common/modifiers, names from the English localisation; Crusader Kings III 1.20.1.2. The DLC is our reading of the code in the rule's key: the file's own dlc lines are commented out.