Quite simply, some stuff i don't know and would like to see whether other people do? Mostly it's oak related questions, as ive found him more enjoyable to play then regulus. 
1. Do oaks spirit wards use the same "souls" as nightwalkers?
Had a 2v2 panth fortress, 2 oaks vs 2 erebus minions. Stumbled upon the fact that the erebus was not gaining as much of an army when the soldiers were being converted into our spirits. So spammed the multiple(4, which gave off extra aoe armour later) spirit wards around the place as a counter to this. We eventually won, as they didnt focus as much on investing skillpoint in survivability. Pretty fun game.
So any truth to these thoughts, or just idle fancy?
2. Is it only level 3 shield or over that cannot be interupted?
I'm pretty sure a lvl 2 shield stopped an interupt before, but i might have bene mistaken.
3. Does rooks god strength upgrade give him cleaving ability? If so how much?
Whilst i originally thought rook had cleave from the start, it sorta looks like he only gets it after god strength.
Does more god strength grant more cleave?
4. Do tower damage upgrades or building hp upgrades stack?
Or is it like the +gold/per second upgrade and is non cumulative?
5. What are the effects of a trebuchet shot other then the damage?
Is it a slow, or a mini stun?
thankyou in advance for any help, from a time-deprived demi god player.