I don't really use them. They are supposed to be good for taking out the crew of a ram (hide both sides of the gate, drive the crew off and escape into the town for example) and they are fairly useful for tactical ambushes, but for the cost, unit size and upkeep, you'd be better off with heavy infantry.

It's a little known fact that Arcani destroy chariots.

Arcani are awesome. They can hide ANYWHERE, so if you dont move them, no one can see them, run like the wind, and can mince just about anyone in hand to hand. Best used in my experience as flanking troops to ensure the obliteration of the enemies hardest units. Not sure of the stats on this, but they seem to make enemies leg it faster than most too. Granted they are expensive, but in the late campaign(especially during the civil war as the other factions dont seem to train them) for me they are a must have, specialist section of the army. If you want a real laugh and can afford it, train a full stack of the little beggars and romp around slapping all comers! Well, I like them anyway.

I do that same strategy, Andro, but with cheaper units. As Germans on the campeign, I would get night raiders and skirmishers and hide them in forest on the campeign map. They would ambush any army that came by, and would massacre them easily.

Arcani are good against chariots? Wow...

Arcani were a secret police force that was looked down upon somewhat because they were kinda like the gestapo. They were I think formally organised by augustus , not to sure about that, but were disbanded due to populer demand.

Also, I didnt know anybody could be put outside walls in sieges, new to me

They are good for the hammer and anvil taktic, can hit enemy from behind on the flanks.

Good in gateways, can be usefull to scare enemy and have a good set of fighters in there

From what i know, the Arcani's where spies. And not deployed in battles.

The Arcani are attested to only once in a short notation by Ammianus Marcellinus and they acted as foreign spies. He indicates that they were in existence under Constans but that they had been 'established in early times'. By the late 4th century Theodosius) they seem to have become unreliable and were disbanded.

Incidentally, Areani seems the more reliable spelling.

Bah, wiki-nerds