Alright I'll try to be as genial as possible in explaining.

In the End Game with Caelum you are using a conjunction of A.) Iceclads (If you have enough production to really utilize them, and your domain is fairly widespread) B.) Blizzard Warriors (For more suvivability and after you have such spells as Wind Guide, Orb Lightning and such) C.) Spring Hawks and Winter Wolves, various other summons. D.) Mammoth/Wingless/Temple Guards. This is the 'meat' of your army, for when your opponent has countered your raiding and starving/diseasing tactics (along with your mages).

Unless your opponent is playing with alot of Nature or growth, they will be hurt by the inability to really quickly reinforce, hold outlying provinces and spending money on Province Defense that you can defeat anyway with a properly made raiding team.

You on the other hand will have the ability to reinforce virtually anywhere, have access to some of the best magic and mages, and able to counter what you are weak against with your land armies (that being arrows, fire magic).

You more than likely are going to have more money and more security than your opponent as well as a better research tree. (This is on average)

That is what the end game is like for Caelum, you are picking away at them until you can steamroll over them.