I played a mission with a hero, and I don't know what I would have done without Spiritual Link (in the original version, this skill is in Darkness).
I don't know if anyone else has done this – at one point, my Markel had 122 skeletons, and my heavily upgraded Godric had 20 angels and 300 pikemen.
The skeletons were standing in a corner, a summoned phoenix was covering them, the hero cast Heavenly Shield, and Spiritual Link was used on the angels.
And then – it was just hilarious. We cast Raise Dead on the phoenix!
The phoenix's health doesn't decrease because it doesn't die.
Maybe this is only in my version (1.2).