Best about those two, they are always in the game and they have become essential to my strategie (which helped me beat impossible in 24 days)
Little example:
Its an ok unit with fairly good initiative and speed and 0.21 average dam/leadership (Green Dragons for an example have 0.06 and Ancient Ents have 0.1) and of course "No retaliation"
Now with those 2 items from above
This is a killer unit. 9 Init and 8 speed beats black dragons and will always be first in battle. Allowing the unit to basically fly over the entire battlefield at will. Morale is at max allowing the unit to crit more often and the unit now deals an amazing 0.36 damage/leadership. Thats 6! times the amount of damage a stack of Green Dragons would do with the same leadership requirement. This is basically like a ranged unit.
After those two the Dragon Slayers sword, Raghas Shield and any item that adds 1 to damage (there is a dagger in the game with +1 poison damage)
Another +1 damage would give those Fairies more than 0.5 dam/leadership. I have seen these stacks doing more than 20k damage on critical hits.