Difficulty

Changing the difficulty doesn't actually change the intelligence of the AI, it only changes the bonuses given to the player and computer controlled factions.

Effects

Newbie

• Player
  • +5 on cities and districts
  • -25% expansion disapproval
  • -25% Hero Upkeep
  • -50% Military Upkeep
  • +20% Unit Health, Attack, and Defense
  • +1 FIDSI per Population
  • +2 Base City FIDS
  • +20% City FIDSI Output
• AI
  • +10 on cities and districts (no with ELCP)
  • +25% expansion disapproval
  • -10% growth, research, buyout, production, and empire plan cost reduction
  • -1 FIDSI per population

Easy

• Player
  • +10% City FIDSI Output
  • +1 Base City FIDS
  • -25% Military Upkeep
  • +10% Unit Health

• AI
  • +10 on cities and districts (no with ELCP)

Normal

• No Player bonuses

• No AI bonuses

Hard

• No Player bonuses
• AI
  • -20% upkeep costs
  • +10 on cities and districts
  • -20% expansion disapproval
  • 15% research cost reduction
  • 20% empire plan cost reduction
  • 20% growth, building production, and buyout cost reduction
  • 20% unit cost reduction
  • +0.25 FIDSI per population
  • +50% strategic resources

Serious

• No Player bonuses
• AI
  • -35% upkeep costs
  • +10 on cities and districts (In ELCP bonuses to Approval have been reduced slightly)
  • -35% expansion disapproval
  • 20% research cost reduction
  • 35% empire plan cost reduction
  • 35% growth, building production, and buyout cost reduction
  • 35% unit cost reduction
  • +0.5 FIDSI per population
  • +100% strategic resources

Impossible

• No player bonuses
• AI
  • -50% upkeep costs
  • +10 on cities and districts (In ELCP bonuses to Approval have been reduced slightly)
  • -50% expansion disapproval
  • 25% research cost reduction
  • 50% empire plan cost reduction
  • 50% growth, building production, and buyout cost reduction
  • 60% unit cost reduction
  • +1 FIDSI per population
  • +150% strategic resources
  • +10 and +50% XP on unit creation
  • +50% XP per turn

Endless

• No player bonuses
• AI
  • -70% upkeep costs
  • +10 on cities and districts (In ELCP bonuses to Approval have been reduced slightly)
  • -60% expansion disapproval
  • 30% research cost reduction
  • 60% empire plan cost reduction
  • 60% growth, building production, and buyout cost reduction
  • 70% unit cost reduction
  • +2 FIDSI per population
  • +200% strategic resources
  • +10 and +100% XP on unit creation
  • +100% XP per turn

Editor Notes: I verified all these values in the game code, though there are some values I didn't put up here that may need to be added.

• The AI At all levels has a 0% chance at getting quests from ruins, and a -40% ruins loot modifier
• Urkan Spawn rates change based off of difficulty
  • Normal and Below: Default
  • Hard: 30% Bonus
  • Serious: 55% Bonus
  • Impossible: 120% Bonus
  • Endless: 175% Bonus