This achievement sounds more difficult than it actually ends up being, so long as you carefully follow the guidelines set out in the achievement description.
To break that down:
- Only lose harvesters through self destruct:
This means that you cannot lose harvesters to the mist when they naturally fall, and you also cannot lose them to enemies conquering the tile. You will obviously want to get the most cash out of each harvester that you can however this can also mean self destructing harvesters a turn early if the CPUs have loaded cannons that might put your tiles into the mist.
- Own one or more each turn:
Naturally, as you will be having to put your harvesters into the mist yourself, you really do not want to own more than one a turn anyway. If you read this very carefully however, you'll notice this does NOT say anything about the start of your turn. What this means is that you can squeeze more turns out of this requirement by NOT placing new harvesters the same turn that you destroy one. Destroying a harvester counts as owning one on that turn, and making a new one counts for the next turn.
Having said that, you are going to want to set up a 4 player match on the Pirate's Cove map, using all skilled opponents. At first glance this map seems like a bad choice due to the starting positions of each player, but there are two huge benefits to this map:
- The height of most of the tiles on the map are 4 and 5, meaning more turns per harvester.
- The CPU at skilled level is really dumb on this map. Really, really dumb.
To illustrate the second point, play a couple of test matches on the map up to about turn 4. What you'll find is just about every match, at least one of the CPU players will place his first two harvesters such that he is trapped on his starting tile! Not only that but his starting tile ends up being height 1 when the harvesters disappear. This is a HUGE advantage allowing you to take over most of that CPU's part of the map.
What I did was continue to start games over and over until I had a game where at least two of the CPUs did this crazy seppuku to themselves.
When one of these bad AI CPU's is your neighbor, you end up getting all of his land to yourself. So I used what should have been his land as my little harvester area, and my land as troop development.
Since every match is different there is no step by step strategy to win, but here are some tips:
- You will end up needing to build carriers at some point, so plan for that.
- If you keep a carrier 'in reserve' the CPUs will try to build some to match you. You can force them to build carriers this way so that you get them as rewards for conquers.
- Try to avoid building cannons. On this map they are usually too far to hit all the tiles you will need to hit. They also take a bit of time to send one tile into the mist and you will be working against a harvester clock.
- Be mindful to keep 5 gold in reserve on turns when you will need to build a harvester.
- Don't use harvesters offensively (to sink enemy islands) if there is any chance the CPU will take the harvester back. If the CPU is down to just a few tiles he WILL use his carrier to take over a tile that has a harvester on it if they determine it is the best spot, denying you this achievement.
- At the same time, if a CPU flies over to your island be mindful of the turn order and how your tiles will be affected if the CPU decides to self destruct HIS harvesters. I lost a harvester to a CPU this way and had to start over.
- Don't get too excited on the last turn when you are about to win and forget to place a harvester (almost happened to me!).