Loving this game so far. I've noticed a couple of bugs in the story mode though, e.g. i clicked add to story and a picture from a different story came up. Also it seems that if two people add story to the same picture it will overwrite the first caption but put both pictures in.
maybe its just me - but i just got (on a second save file - ie a new game completely) to the altar that should have had the old knight's momento on it and there was nothing there.
Using cavalry with crystal spears you can easily beat anything (including greg). It can take a while but extra tip - if you have a slow computer, scroll down so it isnt trying to draw everything and the battle will go much faster (also against greg - resurrecting all his friends can help speed things up)
A tip for the multi-coloured puzzles: starting by crossing all the number that aren't in the current colour can give you a much clearer picture of which squares you can't fill (mainly because those numbers are faded and hard to see)
What i used to beat the epic yeti (all maxed out):
Heroes: Viegraf the Red, Popo the Epic Dwarf, Kara the Slayer.
Spells: Shield or TimeStop (I prefer Shield because it uses less mana)
Units: Goblin, Mad Bull, Dwarf Engineer, Ka-Boom!, Valkyrie, Sky Dragon.
I sent everything except my heroes right from the start. All the units (except sky dragon) spawn and move reasonably fast so they kept the yeti occupied. I sent my heroes/sky dragon in once Shield was available. With Shield or TimeStop your units will be able to reach the yeti's feet where they'll be too close for him to hurt them (and he wont move until they die). Sky Dragon was good for the waves of regular yetis. Those waves should be the only real problem, but if you keep using Shield you should be fine.