Master of Orion II: Battle at Antares/Killing Space Monsters

Usually, the most attractive planets are guarded by space monsters.

There are six species of space monsters. Four of them have the serious problem of having just one weapon ready to deliver significant damage. This is what makes them rather unfortunate creatures that get wiped out quickly when standing in the way of the players expansion plans than a serious obstacle.

The key to eliminating foes with just one strong weapon is attacking with a bunch of small ships. Since the monster is just able to kill one ship per combat turn, the remaining ones can easily deliver the damage needed to destroy it without the need for expensive protective gear.

The most cost-effective approach is to take frigates with battle pods and load it with MIRVed missiles in racks of two rather than five. Eight of these will kill almost every minor monster and are cheaper to build than the colony ship needed for subsequent colonization. There's one exception, though. The Hydra needs at least 12 frigates or one "heavy armor" cruiser to soak up some damage because of the three independently targetable plasma weapons.

Tactical Approach to Space Monsters

 * Dragon:
 * Hydra: it has multiple plasma weapons that can decimate swarms of small ships.
 * Amoeba: it has an equalivant of plasma web, swarm the monster many missile frigates
 * Eel: the easiest monster to kill, although it has the equivalent of a lightning shield its attack only consist of a short-range shockwave, just fire volley after volley of MIRVed misiiles.

Antarans
Antarans will spawn on about Turn 100 and every dozen turns or so thereafter (randomized) unless they have been disabled via setup options. They charge directly at a system, then attack a single random settled planet before leaving. Warp Interdictors will slow down this approach, giving you more time to react.

In battle Antaran ships are quite tough with very high Beam attack/defense. However, they are hard-coded to self destruct with enough damage or if they are rendered immobile. Antarans use Damper Fields (meaning they take only 1/4 damage + Neutron Beams/Deathrays do not kill their crew) with Xenotrium armor (10x base armor/structure) but no shields. Thus beam weapons are not very effective until you can get your targeting above 100% or so. At that point enveloping (base 4x damage) or armor piercing weapons can work (minus reduction for Damper Field). EMG-MIRVed Nuke missiles have a very good chance at destroying their engines, thereby causing a self-destruct. If enough Tractor Beams are used to render them immobile, this will also initiate a self-destruct. Achilles Targeting Units and/or Structural Analyzers can also work well against Antarans, since they have no shields. Neutron Scanners or better will be necessary to use any missiles against the Antaran battleship-class or higher. Augmented Engines give you that little extra distance to get you in range to take them out quickly.

Early on, a lone missile base (on each planet in the system) can be sufficient to defend against the first single Antaran frigate, but this will not be enough to ward off later raids. As well, most play strategies forego Missile Base in favor of Automated Factories, which precludes this defense for non-creatives unless you can get lucky trading/stealing for it. Thus as long as the Antarans are raiding only with Frigates, it can sometimes be easiest to just let them attack "decoy" planets that you settled so they stay away from your more important ones. Each frigate will generally take out 3 buildings or colonists.

By early-mid-game using ships against them is possible with the right tech: EMG-MIRV nukes or Tractor Beams with enough defensive systems/armor packed in to survive for several rounds of combat should be fine (Reinforced Hull + Heavy Armor + Zortrium armor or better). Just move up next to the Antarans and fire your EMG missiles point-blank directly into their ships to blow the engine. Tractor beams allow you a bit more tactical freedom, as you can immobilize the Antaran ships from a distance to trigger their auto-explode.

Once you've perfected the art of immobilizing the Antarans, if your troop combat rating is high enough, you can try and capture them as well before they go boom. Their Quantum Detonators means there is always a 50% chance of setting off the auto-self-destruct by mistake even on a successful capture. Generally with Personal Shield + Zortrium armor + Phasor Rifle you have an even chance of capturing an Antaran ship if you swarm it and board with 5 or 6 of your own of the same or larger class. Alternatively, if you are using Assault Shuttles, you might be able to muster enough boarding marines to overwhelm the Antarean crew in one large attack.

Antaran Homeworld
Once you have the technology to capture Antaran ships and so thereby gain Damper Field and Adamantium Armor, you are almost good to go for an attack directly on their homeworld. You will also need Dimensional Portal, which can often be gained through tech-trade with other races if you don't already own it. Getting into a fire fight with the Antarans is a recipe for disaster. It is much easier to simply take out their ships through the above-discussed auto-destruct method, and capture the Antaran star-fortress by zerging it with commando boarding parties. You should also have at least Powered Armor, Personal Shield and Plasma Rifle for your troops, as well as a Leader with a Commando bonus. With the above listed tech, the Antaran Homeworld defense force can easily be defeated with the following modest strike force:
 * 6 Battleships: Battle Pods, Troop Pods, Reinforced Hull, Damper Field, Automated Repair Unit, Augmented Engines, the rest of the space filled with MIRV ECCM EMG merculite missiles.
 * 6 Battleships: Battle Pods, Reinforced Hull, Damper Field, Automated Repair Unit, Augmented Engines, the rest of the space filled with 10 miniaturized Assault Shuttles.

Note that the Automated Repair Unit is just there so that taking any damage less than concentrated fire from the Star Fortress will be shruggable. You still have good chances for success without it.

Fire your EMG missiles point-blank into the sides or rear of Antaran ships to quickly destroy them and clear the board during round one of combat. Advance all ships towards the Star Fortress. On round two swarm the Star Fortress with ships, preferably those having Troop Pods. Any ships close enough should engage in boarding Raid parties to try and take out key defensive systems. Once the Security Station is destroyed, simultaneously launch all Assault Shuttles. On the next round your massive Assault Shuttle attack strikes home and overpowers the Antaran defenders. You win.