Fog of War would be really nice for pushing bog trogs as survivable front line troops. The High Reclaimers ash cloud spell would also be acceptable for Rasks Blindwater laughs at range spell.
I have been making a fluff bog trog army - so have been thinking of what a caster for them woul look like- What I'd like to see is---
A ranged weapon that let's beasts charge the target for free
a spell that gives a unit poison attacks
an aoe spell that creates a shallow water ttemplate
a spell that creates concealment
A feat that lets you put deep water templates in his control area - 2-3 5"ers.
Can't be placed on enemy models. With the right beasts it would be a nasty feat and fits the amphibious theme.