Several big changes have been made in this Very Big Update (henceforth called the VBU).
New Game Required!
Unfortunately, to access the new features of the VBU, you will have to start a new game. If you want to continue with your existing game, you can go to "Cyclopean > Properties > Betas" and activate "old_version_09928" so you can finish your current game. You may have to restart Steam in order to see this version in the betas tab.
Bug Fixes
The VBU fixes a number of outstanding bugs.
Visual Bugs
There were a few minor visual bugs, like the boat overlapping things in a bizarre way and walls that failed to stop the player from passing through them. There was also a strange effect that messed up the look of the screen during combat (not the wits event, which is intentional).
Missing Corpses
Some creatures in the overworld were not aligned to the grid properly, so you could not access the corpse after defeating them. Also, if you loaded a saved game in the overworld, corpses would appear, but were no longer accessible. Now you should be able to access corpses, even after loading a saved game. Note once you enter a dungeon, and emerge, the monsters in the overworld are randomized and corpses are removed.
Missing Books
Two books would not load properly in the Crag of the Ghouls. They should appear correctly now.
Attacking Allies
A strange bug allowed hostile creatures to attack your allies outside of an actual encounter.
Traps and Secret Doors
If there was an active trap right behind a secret door, it became impossible to actually detect the secret door.
New Features
The VBU has a number of new features will will dramatically effect the gameplay in Cyclopean. I will try to summarize them here without giving away spoilers. I don't know exactly how all these changes will interact with each other, and with player's expectations, so I imagine I will be tweaking things in the next few days.
Creature Features (like Venom)
More special creature effects have been added. I want these to be a surprise, but to give an example, Ghasts are now venomous (as they are described in the text) so you will want to find some anti-venom (named atterlothe in the game ... an archaic name I feel Lovecraft would have approved of) when you intend to go into the Vaults of Zin.
Other creatures have new unique effects, I will leave the rest for you to discover for yourself. I plan to add more, maybe not for every single creature, but at least two or three more.
Expanded Ally Interactions
Having allies was always an important part of the game, and since the beginning, each type of ally would give the player certain bonuses to things like stats.
Now this system has been greatly expanded upon. Each kind of ally will have an additional, stacking effect, depending on the other allies in your party. For instance, having cats and ghouls together will give you a limited night-vision in dungeons, which lets you take advantage of the darkness bonus, while still being able to see (though not as well as with a torch).
These relationships are described in more detail in the inquiries panel, so make sure you ask your allies about the other creatures in the underworld. Note: not every creature is aware of these effects, so you will usually only learn of an effect from one of the two parties involved.
Camp Fights
Also, some allies who are hostile to others will no longer join your party if their enemies are present. Also, if you do have alliances with two or more hostile groups (which is still possible) they won't like if you leave them together at camp, and will begin fighting.
You can keep hostile allies in your party as long as you keep them separated, i.e. cats in the tent, and zoogs in your party, so you can switch them out as needed. Good luck!
New Items
A lot of new items have been added, most notably clothing and armor pieces. Helmets, gloves, boots and more can be equipped, which will improve your protection or sneak stats. Also, the aforementioned "atterlothe" which is a type of anti-venom, will be available.
Artifacts
To dig deeper into the ally features, there are now unique artifacts that provide even further bonuses, but they are rare and there is no guarantee of finding them. The idea is that you may find an item that will provide a bonus from a particular ally type. If you find that item, it may encourage you to seek out that creature as an ally, to get access to the bonus.
Doors
Once you interact with a door, it will "remember" your interaction. So, if you try to bash a door, and fail, it will tell you the minimum strength required to break it. The next time you meet that door, you don't have to try to bash it again, it will remind you what the minimum strength was when you interact with it again. This is the same for the skill+mind requirement for lock-picking as well as key type.
Item Descriptions
Clicking on an item in your inventory will now describe very briefly what that thing does. Armor and weapons still shows the strength or skill requirement as before.
More Corpse Features
Creature corpses will now display the type of creature whose corpse it is you are searching through.
Creature Fights
The creature conflict feature has been expanded further. You will now hear them fighting when you are close, but the sound effects will fade out with distance.
Other Stuff
Other things are included in the VBU, but you will find them as you play. One of the possible "main quests" has been given an additional requirement, a new trader was added, and many things were tweaked in the process of making this update. I hope the game feels more interactive and emergent. Have fun!