The Patchlog is by far not complete. There will be changes in a few areas.
Barbarians and Wilderness
A Wilderness mechanic is added that regulates what kind of creatures you will meet. At the moment time limits the spawning of creatures (many will only spawn later in the game), in 1.3 spawning of creatures is limited by space. Near your starting point you will only meet goblins, skeletons and other easy prey, but the further you go out into the world, the more dangerous creatures you will encounter. Acheron for example will now spawn in places with a high wilderness level and roam freely, but is limited to places with a high wilderness level, so you won't see him anywhere near your starting location ever. Same rules are applied for AI starting locations.
Barbarian Lairs have less defenders and from time to time groups of Barbarians spawn that will perform some missions. Goblins try to pillage stuff, but quickly run from danger, Orcs try to raze your cities, no matter how heavily defended they might be, Necromancers travel with some skeletons as protection and perform dark rituals in your lands if you don't stop them, etc.
Animals are less of a threat now. They are at peace with barbarians now and there aren't any animal lairs anymore.
Many resources are also placed only in regions with a specific wilderness level. For example you won't be able to find mithril next to your starting city, you will have to travel to dangerous places to mine some.
First Balance Pass on Civilizations
The following list is not complete yet
Amurites
Aptitude from Swordmages/Battlemages/Planeshifters removed
Battlemages and Planeshifter have an Arcane Aura like Mages (allows them to cast spells)
Govannon Production cost reduced from 480 to 300
Firebows have Base Combat Strength 5 (+1fire)
Swordmages have Base Combat Strength 4
Mana cap increased by 50
Amurite Leaders start with the Arcane Trait
Amurite Civtrait gives +30% Spell Research on top of the bonuses given by the Arcane trait
Bannor
Clerics have a Combataura(Strength/Healing/Bonus vs. Evil) instead of Healing Spell
No limit to the Amount of Clerics that can be build. Clerics require Order Religion. Basically Clerics are now the favorite Tier2 Unit for Bannor and give Bannor a huge synergy with Order Religion.
Benevolence Civic(virtue) added. Increases Health per Culture Level of City. Req. Good and Way of the Wise. All civs can use it. High upkeep
Crusade mechanic redone. Crusaders now spawn in cities and in groups to reduce micromanagement. They also start with good equipment. Spawn number still depends on number of town improvements (see crusade pedia for spawn details)
Building restriction removed from Crusade. Instead Crusade now gives a static science penalty. (much easier for the AI to understand)
Calabim
Feast is a Global Enchantment (reduces Population in all cities, increases experience of all Vampire Units
Doviello
Scavenge mechanic: Doviello repair their Equipment after battle if defeated enemy has Equipment
Elohim
Purity Counter is increased by 7% for every Unique Feature sealed
Monks can not use Weapons/Armor, but have higher base strength(depends on purity counter). Monks also provide faith income.
Hospitalier metal requirements removed
Frozen
Ice Golem starts with Cold Resistance
Ice Demons are considered "not alive"
Grigori
Only Grigori have access to the adventurers guild
Grigori have special Equipment for Heroes
Luchuirp
Barnaxus starts with Hero Promotion
Illians
Temple of the Hand gives 2 Faith
Samhain, White Hand and Deepening are Global Enchantments(thus repeatable) and cost faith instead of hammers
Sidar
Waning is a Global Enchantment. Reduces Experience of your units. Creates Shade Units proportonial to the Experience lost
Improvement System streamlined
hard cap on the number of improvements that can be build per city (currently 4/7/10 for city with radius 1/2/3)
plotinfo displays the amount of improvements that can be added to a city
Great Person Spawn Function reworked
The idea is to create a system where a Player has more choice on how many Great Persons he will create in a game. In future Patches Great Persons will get more interesting abilites.
Cost of Great Persons increases at a lower pace
Culture and Population above 10 of a City modifies how many Great Persons a City produce
Faith
Most disciple Units provide a Faith income instead of upkeep
Faith can either be spend on short term miracles (like Bless for Order), or used to purchase sacred Knowledge (Techs that can only be gained by Faith)
Religion Techtree reworked (all techs needed to spread a Religion have only mysticism as prereq)
Priest Units have a Combataura (from Esvaths mod merged and modified)
Equipment
See other thread
Economy
The economy is heavily modified. The productivity of cities now depends a lot more on the number of buildings they have.
Food and Health are more important. More food is needed so that a City grows. There are new ways to use food.
Unit Supply Limit: the gold cost mechanic for units outside of territory is removed. Instead there is a hard limit that can be increased by buildings (and is modified by civics/traits)
lots of buildings added
Several buildings now have advantages and disatvantages so you don't want to build them in every city
Some buildings consume Resources so you can build them only in a few cities (these buildings are typically very powerful)
Allmost all resources now have effects that stack (that means it is useful to have multiple resources of the same type)
Universal Happiness boosts (those that do not come from buildings) are very rare now (and much more powerful)
As a result City size will vary a lot more.
There is a new City specialization mechanic now (works passive). Cities will specialize into what they are doing. Cities that produce many military units will give new military units free xp, Cities that produce a lot of gold will get a bonus modifier % to gold production, etc. Processes like wealth can further increase the city specialization.
Expansion is now limited by gold rather than production. Settlers always cost 120 hammers. However Cities have much higher maintenance costs and there is a much higher incentive to improve cities instead of spamming them.
Balancing
several modification to Summons
Tame Animal mana cost reduced to 30
Create Lumber, Leather etc. only give 100 instead of 600
Ranged attacks by archers cannot target cities
Damage dealt by Archers in Ranged warfare reduced (normal archers have a cap around 20%, later units 30%, hereos a bit more)
only earlygame techs can be discovered by goody huts
several changes to the techtree. costs of tier3 military units (champions, rangers, etc.) a lot more similar.
heal after combat (for example cannibalize) is triggered only after attacking
Fixed
Improvements will only modify adjacent Improvements if both improvements belong to the same city
Improvementyieldchanges are applied only once to adjacent tiles (cottage for example will only get +1prod, even if adjacent to 5 quarries)
Pirates do not spawn in ice
Issue with Sanctify Ritual and Haunted Lands
Elemental Hordes won't split anymore
Angels can't be sacrificed anymore on the Pyre Improvement
Chain Explosion costs 20 mana instead of 60
City Growth Notifications aren't shown if the City is set to stopgrowth.
DamageResists are correctly applied (10 points of resistance reduce strength by 1)
issue with "no new random seed on reload" fixed
Documentation
Actual Damage Resistance shown in Combat odds Display
Spellresearch has a Popup like normal Research (if no spellresearch is currently selected)