How to get the There Is No Greater Ruler Than Thou achievement.
Trying to beat the game in a single reign can be a pain. Here are some tips if you're struggling with that. There might be other strategies but this ones worked out for me really well.
1. Be quick. The greed attacks get stronger the higher your day count is, so don't lose time.
2. Island 1-3: Destroy all small portals on the cliff side and then leave ASAP. The counter attacks get stronger later in the game, so better destroy the small portals early. You will appreciate later that you just have to place the bomb when you come back.
3. Island 4/5: As soon as your defence is okay: Attack! If your squire/knight did a good job with a small portal, just send him out for the next one the day after. When a portal is close by: One knight/squire with his squad should be enough. For the really far ones you should use two.
4. Don't destroy any portals on the dock side! Every destroyed portal results in the greed attacking more aggressively, so don't annoy them more than necessary and don't waste your time. You don't need the lighthouse anyway!
5. Defence: Make sure to leave the outer walls on the highest possible level when you're about to travel to the next island. Try to ensure that either an archer tower or a ballista is protecting that wall. On island 4 and 5 up to day 120 the combination iron wall, 3-4 archers and a roofed triplet tower or ballista was totally enough to even defend blood moon attacks.
6. Don't worry about decay. When you're fast, decay shouldn't be a problem. You have the whole day of your arrival to rebuild the two outer walls and maybe even to upgrade it. Again: No lighthouse needed.
7. Attacking the cave: When you plan to attack the cave and place the bomb, make sure you have two fully buffered knights with a complete squad of 4 archers each. Wait with them until the night wave is over and then leave instantly. Don't bother expanding your base close to the portal. I did that first to avoid running into the next attack wave. It takes too much time and is not necessary! As long as you're not unlucky to run into a blood moon attack or you destroyed too many portals, your knights can handle that. (I ran into an attack on island 5 day 120 and it wasn't a problem). Make sure to leave with a full pouch to buffer your knights after an attack and in the cave.
8. Statues: The only ones you definitely need are the archer statue on island 1 and the builder statue on island 3.
9. Hermits: I took all of them with me, but in the end I just needed the baker once. They're not mandatory to beat the game, as long as you're not too unlucky and your Vagrant Camps are really, really far away.
10. Mounts: Use the stag for the first year to make extra money by charming deer. But as soon as winter arrives, dump it for the Griffin and keep that one for the rest of the game. In my opinion it is the best mount to successfully escape the cave.
11. Money: Don't waste your money on the banker. Spend it all. Quick progress is necessary. I also didn't build any farms, since there aren't even any close to your base on the later islands. I got all my money from the bunny/deer hunt and the pikemen in winter. Make sure to build enough of them in time.
12. In case a time schedule seems helpful for you: I spent the first year with preparation and destroying small portals. On day 53 I cleared the first island and on day 124 the last one. On each island I destroyed the cave around day 20-25 local day count. With this speed I managed to avoid confronting breeders and crown stealers totally. I traveled to the islands in this order: 1-2-1-3-4-1-2-3-4-5