Necromancer – “Ruler of Erathia” [Campaign 3, Mission 5]

Regarding Isabel losing units to Godric, I simply resolved it like this: let's say griffins left – I loaded an autosave, placed the griffins in the castle, and in the end, on the designated day, they told me that the griffins had flown away, but in reality, they were all still in the castle!
And I won the last battle simply by using resurrection! By the way, those who haven't noticed, patch 1.3 reduces the unit's health by 20% for each cast!