One of the most annoying defensive/offensive structure is the Aramonian Trebuchet and Creon has a problem dealing with them, like any other Kingdom of course (Veruna, Zhon, Taros). Here are some tips which I hope will help to deal with that menace.
1] When you see your ground units or structures to be hitted by something that looks like an extremely-fast moving cannonbal it is by 95% a Trebuchet. The first thing you should do is to detect the way from where that "cannonball" came. It is not an easy thing to detect its coming direction, you actually can only notice the moving Trebuchet's projective just before it hits you, but you must!
2] After detecting its direction, quickly create an aerial scout (Barnstormer in Creon) and send it flying towards the Trebuchet's direction. Sooner or later, you will notice a big wooden structure with a round stone base. This is the Trebuchet. If your Barnstormer is killed by Archers or something else before you locate the structure, make a few more Barnstormers and send them all together. Luckily, someone will survive to see the Treb's location.
3] Deal with the problem! Destroy the Trebuchet!! This may be an easy or an extremely difficult task, depends on how well the Aramonian player guards this engine of destruction. The most common way is to create a dozen of high-range units (Tortoises and Beast Riders) and send them alltogether against the Treb.
4] In case the upper strategy doesn't work because the Aramonian ground defenses are too strong (many Strongholds or a lot of infantry for example) or because the terrain makes it impossible (aquatic maps for example) you should make an aerial assault using the only aerial offensive unit available (Neo Dragon). Create a dozen of them. Since the Aramon has no offensive air units at all, you will probably encounter minimum resistance while your Neo Dragons fly towards the Trebuchet and burn it down with their blue flames. However, a group of Guard Towers and Mage Archers can wipe out your Neo Dragon fleet fairly easy, so be careful!
5] In some cases the best way to destroy an Aramonian Trebuchet is the Creonian equivalent of the Treb, called Prismatic Mirror. Create one or two of them and burn the Treb without mercy. Just make sure that there is no wall or obstacle between the Prismatic Mirrors and the Treb, because Prismatic mirror's light beam cannot travel above walls. Just create them as fast as possible (the use of multiple Mechanics is highly effective here, if you have the mana of course). Don't forget to protect your Mechanics with some guards (Automatons may be the best choice here), because the Mechanics would not stand alone against an attack of not freezable units. I suggest to use this strategy only if the above ones have a very low chance of success.
6] In an aquatic map, if the Trebuchet is near the coast, things may be easier! Creon has a naval fleet of really powerful ships with a good fire range and a few of them will blow up that annoying siege engine into seconds.
7] Destroying the Trebuchet with a Creonian Bomb Sprinkler may be the fastest way to get rid of him. When you construct the Bomb Sprinkler, it will blow it up with extremely speed by continously firing bombs to it! The difficult part is to construct it fast! Use again a lot of Mechanics and protect them with Automatons and other units untill they finish.
8] Here is some extra info about the trebuchet:
* Trebuchets cost more than 10000 mana and are slow in production, so if you destroy it before it act your opponent will lose a lot of time and a lot of mana for nothing!
* Trebuchets have tremendous range! In small maps, they can easily hit any ground/naval unit or building. However, they cannot hit aerial units and in big maps you can keep your ground/naval units safe by leading them out of the Treb's range.
* Trebs are rediculously fragile. It is by far the Aramonian building with the less hit points (if you exclude Lodestones), so they can be destroyed really fast.
* Aramon players usually use Flying Builders to construct Trebs to the most unpredictable places. Always search every single inch of the map for Trebuchets, you never know where they may be...