Ring of Friend Shield

[Gwiber]

Ring of Friend Shield

These curious rings always come in pairs. A ring of friend shield without its mate is useless. Either wearer of one of a pair of the rings can, at any time, command his ring to cast a shield other spell with the wearer of the mated ring as the recipient. This effect has no range limitation.

"Either wearer of one of a pair of the rings can, at any time, command his ring to cast a shield other spell with the wearer of the mated ring as the recipient"

What happens if one wearer casts this using the ring? And then the next round the other user casts it using their ring?

Would you more or less effectively have two people sharing the same combined Hit Point Pool?

I mean if one person were to take damage, it would drain from the other as per the spell to help heal...

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and vice versa.. Which could either mean they have a single HP pool; or the effect could cascade and kill both of them as the spells drain from each other to repair the damage... oh.. that thought... that's nasty.

[blahpers]

This question reduces to "What happens when two casters cast shield other on each other?"

Suppose Fred and Ned cast shield other on each other. Then Bob hits Fred for 16 damage.

Fred would take 16 damage, but because of shield other he takes 8 and the other 8 go to Ned.
Ned would take 8, but because of shield other he takes 4 and the other 4 go to Fred.
Fred would take 4 damage, but because of shield other he takes 2 and the other 2 go to Ned.
Ned would take 2, but because of shield other he takes 1 and the other 1 goes to Fred.
Fred would take 1 damage, but because of shield other he takes 0 damage (always round down) and the other 1 goes to Ned.
Ned would take 1 damage, but because of shield other he takes 0 damage (always round down) and the other 1 goes to Fred.

...

Hmm. This last part is a bit of a problem. Nobody ever takes that last point of damage because you always round down and send the remainder to the other. *shrug*

Realistically, I'd simply disallow more than one redirection. In that case, Fred would take 8 and Ned would take 8, full stop. But I don't know if that's the intent.

None of these things are quite a shared hit point pool, as the character with fewer hit points to start with will fall first, but it's still handy--especially if they both have DR.