There's four ways to die in a battle and get a second chance I know of.
The Life after Death battle spell.
Everyone that dies rises again as zombie
in the same battle. Commanders keep all their item (*). If he survives with his shiny new rotting body, he is there the next turn. Stats change but magic does not. Some players use this to let their researchers research for free.
A global (Haunted Forrest I think)
Everyone that dies rises as a Carrion beast or Manikin. However if he survives the battle he's still lost, dissolving or following the order of a mysterious ancient power, I don't know.
The Ritual of Rebirth ritual.
The mage with that cast on himself returns to the cap, when he dies as wight mage. Only if the battle is under friendly dominion, though. All items are lost, I'm quite sure.
Shapechanging
Some units have a second shape, that mysteriously appears after they've been killed (well, it doesn't matter wether they are only stabbed or a 5 ton meteor drops on their head
). Werewolves for example.
All items are kept. (*)
(*) Except for those that the new shape can't carry. For example if a wyrm with 2 heads ends up as zombie with 1 head 1 helmet is lost.