OK, here are the stats on the enternal knight, which is infantry and does not fly:
HP - 14
Prot - 12
Morale - 30
Magic R - 14
Str - 12
A - 12
D - 12
Precision - 10
Move 2/10
It also is sacred, has 100% fire resistance, and regenerates 2 HP per turn.
They are led by a powerful priest with the flambeau, which does 13 AP damage and also casts the holy pyre spell.
Not bad, and it would be nice if I could recruit those eternal knights there when I take it and build a temple. But I really doubt that will happen.
I have decided to attack it with my god and 8 archers in 4 squads, hoping to kill the priest with proper battlefield management and good scripting. Since there is only the one commander, I hope to get them to retreat by killing that leader quickly.
Of course, I could lose my pretender and be just like my neighbor Vanheim.
More likely, if it fails, I will lose my archers and the God will safely retreat.