(based on my older suggestion of the same name
A larger-scale version of (in)famous Territorial Control, the Conquest.
Just like the Horseman of The Apocalypse from the Bible.
Conquest is unique in the way that instead of taking place on one map per round (in this case, "Grand Round"), Conquest is a gamemode stretching over multiple maps.
Usually, it plays TC on individual maps, albeit this may vary per server. (CTF is also a possibility, see below)
At first, there are 5 (can be more or less, but it's always an odd number - 3,5,7,9) maps, with an even numbers of them per team, and one neutral map.
The neutral map is the one the first round takes place on.
BLUE - BLUE - NEUTRAL - GREEN - GREEN
The team that won the round on the map has taken it over.
Conquest partially takes place in "turns".
The outcome of the battle over the neutral map will decide which team takes the turn.
Let's imagine that Blue turned out victorious. In that case, it's Green team's turn.
During a team's turn, there are two options (chosen in a voting)
They can either:
a) try to capture the lost map back
b) prepare the next map in turn
When trying to capture, the round will take place on the Blue's map, in the state it was left after last round.
When preparing the map, the preparing team is given X amount of time (set when starting a server) to freely build around on (better utilize this time strategically), without the opposing team threating them.
In the meantime, the opposing team has (limited, open to suggestions) spectating abilities.
Once the attack/setup is over, it's the other's team turn and they have the same choices of either setting up the map for upcoming attack or assault the first map in line.
Should the battle take place on the team's last map, there is a timer - if the defending team manages to not lose when the timer runs out, they are considered winners (of that round). The timer can vary (set when starting the server).
Maps that the battles take place on can be either generated or choosen manually.
During setup, only half the map can be built on (the other half is where the opposing team arrives during the attack).
To prevent "stalemates", a team can't choose setup twice in a row.
Kiind of rushed this one, though.
Sorry.
(I'm not playing the game nearly as much as I used to, so I don't know whether this would still work or not)