Star Gate to the Ancient Battleground

Star Gate to the Ancient Battleground
The Star Gate to the Ancient Batteground is an activity that you can take place in from the Defense tab of the menu. It is a combat activity where you choose from different ranks of battles, each with different levels within them determining the difficulty of the battle. Below is a table of the amount of enemies in each level ( info from S16 - Pavo, S15 - Lupus, S14 - Draco after 2013-01-10 patch).

Early Tactics
You can create a force capable of eliminating level 1 or 2 without casualties, consisting of just a basic flagship (with repair upgrade) and a single wind fighter. You will need a raw midshipman promoted once to sub-lieutenant to take a flagship. This fight takes a long time to end (use the big blue X in the lower left of screen to skip ahead). This is probably the lowest use of fuel per combat (but experiment because early on you'll have plenty of fuel). The cooldown time per combat increases over the day (starting at 6 minutes, 6, 6, 9, 9, etc).

Rewards
At level 1-5 you get an extra reward (of Kit 1) at a rate of what seems to be 10% per level of the fight. eg 20% at level 2, 50% at level 5. If you have spare equipment from the kits they can be sold (under the assets menu / commander tab / recycle button) for 800 of metal or crystal (40% chance each) or 200 Nova coins (20%).

At level 6-10 you can gain a Lion flagship blueprint. You need one per Lion you build.

At level 11-15 you have a chance of tech scroll 1 which can be used to create Core Tech which is needed to expand to more planets.

Multiple Forces
From level 6 the Ancient Battle Ground forces are divided between multiple fleets. You can field several fleets too although based on the random starting positions, one of your fleets may end up fighting several enemy forces or vice versa.

Enemy Force Table
Note these forces seem to be out of date beyond level 5. The battle simulator's data seems better. Raptors were reduced and Vulcans increased. Note that force 1 is raptors and vulcans, force 2 is eagles and tempests.