Sacred Units!!

[Micah]

I'd much rather grab soul vortex than a spell that's easily countered by a storm (mass flight) and requires A4 when your leaders only have access to A1. At that point you'll also have arrow fend, making mass flight to counter flaming arrows somewhat redundant. Not to mention that flying units tend to get split up out of formation, which seems like a bad thing for the giants. Plus it's level 7 research compared to Flaming Arrows at level 4...

[Shovah32]

Flight, on the other hand, is much lower research and only requires A2. It only works on a single unit but with niefelheim that isnt too big a problem.

[HoneyBadger]

A Niefel Jarl doesn't get split up out of formation-a Niefel Jarl *is* the formation

[Jazzepi]

The only way to split up a Jarl's formation is with the edge of a sword.

Jazzepi

[Valandil]

Or a rain of astral rocks.
Stupid Druids.