Galactic Civilizations II: Twilight of the Arnor

Overview

Twilight of the Arnor is the second expansion pack for Stardock's popular 4X strategy game Galactic Civilizations II.  With a dozen new race-specific technology trees, additional fleet-level combat tactics, drastically improved graphic textures, a new type of victory condition, an updated planetary invasion screen, and a host of editing tools for modding every element of the game, it overhauls so many gameplay features that it could have been marketed as a sequel in its own right.

Arnor requires both the original GalCiv2 and the Dark Avatar expansion pack in order to install. 

New Technology Trees

The single most significant change introduced in Arnor is the inclusion of different technology trees for nearly every faction in the game.  Custom tailored for each race based on its back story within the GalCiv universe, these new research paths lead to dozens of unique ship components and planetary improvements that fundamentally alter the way that each race is played.  There are simply too many changes to describe in full detail -- so many that as of August 2008, Stardock itself has yet to publish a full catalog of all the differences -- but a few notable examples include:

• Arceans eschew the development of faster engines in favor of colonial Navigation Centers that will permanently boost the speed of every space-going vessel produced on that world.  This encourages them to further specialize their manufacturing worlds with these structures, and though this can give them a valuable speed boost in the early game, their ships are often noticeably slower than the races who eventually discover better drive systems.
• The Drengin's extensive use of forced labor lead to Slave Pits which are more cost-efficient than the traditional factory, but incur a cumulative penalty to their cultural appeal and makes them more likely to defect under the influence of a foreign culture.  Fortunately for them, the money they save with unpaid workers can be used to field large numbers of powerful warships, and early access to advanced invasion technologies give them some of the most savage ground troops in the game.
• Torians breed so quickly that they're practically born pregnant, but because they were essentially a preindustrial society when they were first conquered by the Drengin, they struggle to master scientific advancements that come easily to their neighbors.  Instead of dedicated research labs, they start out with more primitive universities and must take full advantage of their astonishing rate of population growth to close the knowledge gap.
• The Iconian Refuge enjoys early access to powerful weapon systems and regenerative hull plating, but because these are the remnants of another, more advanced civilization, they need to reverse-engineer the underlying principles before any of these technologies can be further improved.
• As a synthetic race, the Yor replace traditional farms with Energy Stalks which support larger populations and higher morale bonuses which both lead to more taxable income.  This provides the funding necessary for their incredibly efficient military and domestic production as they crank out new factories and interstellar vessels with astonishing speed.
• The Thalan have arrived from a time in the distant future when habitable planets are virtually nonexistent.  The very concept of terrestrial colonization is foreign to them, so they begin the game without access to factories, laboratories, or economic centers of any kind.  They breed very slowly and their inability to ever discover farming technologies keeps their population density low, but they can offset their meager tax revenue with the construction of uniquely potent starbases to maximize their productivity and trade income.

Since the layout of these tech trees was inspired by the historical and sociological background of each species, players will find that the Korath have a great deal in common with their cousins the Drengin, as do the Altarians and the Drath who both evolved on the same world.  The Terran Alliance, meanwhile, navigates a technology tree most similar to the generic one that all the races used to share, though even they have a few new branches to explore.

Certain race-specific research is flagged as untradeable, so the Arceans cannot offer the unique bonuses granted by their "Glorious History" in exchange for those bestowed by the Terrans' "History of Extremes."  Another wrinkle in the texture of the gameplay is that empires may no longer hold onto colonial structures they don't have the research to operate properly, so if the Drengin conquer a Thalan world covered with insectoid Manufacturing Hives and haven't previously traded for the requisite technology, the Hives will all be immediately torn down.

As with ship styles and Super Abilities, custom created races are free to adopt any of the specialized tech trees as their own during the setup phase of a new game.

Other Additions & Tweaks

Beyond the specialized tech trees, Arnor includes a wide range of other new gameplay mechanics such as a fresh victory condition, more fleet tactics, overhauled graphics, and an enormous new galaxy size.

Terror Stars

These moon-sized vessels are slow, defenseless, and extremely expensive to research and develop, but the civilization that can maneuver one into firing position near a star will trigger a devastating supernova that reduces the local planetary system to a field of debris.  Completed Terror Stars take a minimum of ten weeks to come online and can only take a single move per turn so its unlikely one empire could catch another off-guard -- they're mostly intended as a last resort game-ender against a foe whose defenses would be too thick to crack via conventional warfare.

Ascension

One of the major elements of GalCiv2 has always been the exploitation of rare interstellar crystals which can mined by special starbases for an empire-wide bonus.  This new victory condition adds an additional type of resource to the mix: Ascension crystals which, when extracted, starts a civilization down the path of god-like immortality.  Each of the five such crystals can generate one Ascension Point per turn for the owner, and any race capable of defending its mining bases long enough to accumulate one thousand points will win the game.

As with every other aspect of the game, the AI in Arnor has been updated to understand the importance of these crystals.  Computer-controlled factions will not only attempt to seize these crystals for themselves, they'll also grow increasingly antagonistic towards other races who attempt to make progress towards this sort of victory.

Fleet Tactics

Arnor adds several new ship components which enhance the performance of all other ships in the fleet.  These systems are so bulky that mounting them on every vessel is proves wasteful, giving rise to a sort of "command and control" flagship which specializes in automatically coordinating the other members of their battle group.  These components include things like Warp Bubble Generators to increase cruising speed on the galactic map, Fire Control Centers to increase damage output, and Harmonic Defenses to help deflect enemy weapons.

To further specialize ship designs, some of these tactical systems are primarily defensive and only function inside the civilization's own cultural influence.

Enhanced Graphics

Thanks to extensive refinements to the graphics engine, every object in the game sports much higher quality textures than in any previous edition of the game and takes up less video memory to boot.  Additionally, every colonial structure has been redrawn with higher resolution artwork, and the planet surfaces themselves have been completely revamped to make each one appear distinctive.

A new invasion screen replaces the old animation of tiny soldiers and tanks with a "video feed" from the surface showing off the level of destruction wrought against the colony's infrastructure.  Though high in quality, the prerendered animation always seems to play out the same way and doesn't show off any of the more elaborate conquest tactics like Tidal Disruption, Mass Driver Bombardment, or Information Warfare.

Immense Galaxy

For players who relish the idea of an epic 4X strategy game that may take months to complete, Arnor adds an "Immense" galaxy size consisting of a whopping 576 sectors, each one of which is twelve spaces on a side.  These maps are so big that Stardock had to reengineer the AI to do battle against enemies that might take upwards of two dozen turns to even reach, reteaching it how to design its own super-long range ships, establish starbases as resupply points, and manage its economy on such a vast scale.

Trivia

• As with previous iterations of the game, Arnor includes no copy protection to prevent it from being downloaded and installed on multiple machines.  It must, however, be registered with Stardock in order to receive any of the bug fixes or other enhancements which have come out since its initial release.
• Every player who prepurchased the expansion pack was invited to participate in the open beta process and make bug reports and suggestions in a dedicated forum on the game's main website.  Most of the races were disabled at first because their technology trees remained unfinished, but steady updates gradually added more while concurrently making adjustments to the existing ones based on community feedback.
• Despite the lengthy and conscientious beta test, Arnor still shipped with a small number of niggling bugs.  One prominent example was that the Thalan could research several levels of weapon upgrades for their extraordinarily well shielded starbases, but because a requisite technology had been removed from the start of their tech tree, none of them could actually be equipped.  Many such issues were resolved by the 1.95 and 1.96 patches.
• One of the special projects available to races with an Evil alignment is the Mind Control Center.  According to its description, this special project is supposed to grant a 100% economic boost to its home planet and cause foreign planets to defect to the owner's empire much more easily, but neither of these affects appear to function in any version of GalCiv2, including Arnor.  This persistent issue was finally brought to the attention of Lead Designer Brad Wardell after the release of the Twilight of Arnor expansion pack, and he has pledged to address it.
• Stardock has also announced development on a free update for all existing versions of GalCiv2 which will bring them up to version 2.0.  Planned enhancements include further improvements to the invasion screen, a complete reworking of the current espionage system, a full fix to the lingering Mind Control Center bug mentioned above, and more.