I know the campaign starts sometime after attaining Town Tier 2, but so far all i experienced were some favors like the charging stone and the wounded rabbit, the geomancer training quest, and the rabbit residents quest.
I was wondering, how long before I can get to the part where I can fight the titan without doing the orc campaign?
The more quests you fulfill one way or another (helping the rabbits) the quicker the titan quest will arrive. The amberstone quests also have some cooldown time before the next one spawns.
I believe you need to get the Geomancer and unlock some crafting recipes first, once those quests finish you should get the Titan one.