i hope this link helps in explaining both bonuses
Yes it did thanks.i hope this link helps in explaining both bonuses
As sentries are the only thing that increases intelligence bonus, and you can only have 20 of them, the max intelligence bonus you can get is 1000. For defense bonus there is no hard cap, but the highest I've seen on Stormfall was 32k.
I've always found sentries to be a waste though. Most people don't spy before attacking your castle, and the boost you get to intelligence bonus from sentries is far smaller than what you get to defense bonus from ballistas or catapults.
So buying the max amount (20) of level 5 sentries costs 19,200 sapphires, and gives you 1000 intelligence bonus, boosting your spies by 10%.
Building 20 ballistas or catapults costs the same amount and gives you 5000 defense bonus, boosting the defense of all the units in your castle by 50%.
In a large battle this could mean the attacker loses tens of millions in extra offense, as opposed to a few hundred extra spies.