Once out of New Player Protection, any player in Illyriad can be attacked by any other player.
Don’t panic. Unwarranted attacks on new players are very rare. But it is as well that you do defend yourself.
There are several ways to do this.
Mage’s Tower. Building a Mage Tower allows you to research defensive Runes. The killing-variety of Runes (Mark of Slaying, Death Rune, Killing Glyph, Ward of Destruction) are excellent spells – once cast on your city, they guarantee that incoming attackers will take losses. A killing type of rune is your easiest way to gain a little defense. For me, getting to a level 15 Mage Tower and casting Ward of Destruction is a priority when I’m building a new city.
Vault. A Vault protects your goods from plunder and theft. Sounds great. But at high level this costs a lot to build, and protects little, so don’t rely on this once your settlement has grown. But early on, building a low-level Vault means you have a range of resources well protected. Get a Vault and some Runes to ensure that would-be plunderers regret ever attacking you: if an aggressor loses troops and gets nothing from his attack, then he probably won’t bother attacking you again.
Troops and Thieves. The obvious way to protect yourself is by building troops and (because you can also be attacked by thieves) thieves. Obvious, but, for a new player, a bad, bad idea. Unless you can maintain literally thousands of troops, it isn’t really worth bothering with any. (I’m not a particularly warlike player, but my standard city-build still has ~3,000 Advanced Cavalry on hand in case my alliance calls on me to attack someone – as in this image: Established, aggressive players will have much bigger armies.) Small players will be deterred from attacking you by your Runes and Vault. Big players will not be deterred by anything less than a few thousand defending troops. So, postpone building troops until you are well established.
Walls. When you get established enough to maintain a thousand troops or more, then start building them – and at that stage you also want to build up your Wall as fast as possible. The Wall gives a bonus to your defending troops – it’s no use at all on its own, but this gives a bonus to your defenders. (It takes lots of stone to build, so when you’re building at high levels consider buying in stone from the market.)
Alliances. Absolutely the best way to defend yourself, as a starting player, is to join a well-established alliance. Getting into an alliance with a few really big military players means that, while you might only be able to maintain a few hundred troops, you are now linked to players who, between them, could field hundreds of thousands of troops. They can protect you when you cannot protect yourself. But vitally, don’t join any alliance that is in a war, or is likely to get into one any time soon – do that and you’ll just have made yourself a target in other peoples’ squabbles.
So, as a new player, get defensive Runes up, build a low-level Vault, but most importantly, join a good alliance.