4th coldain ring
 

is the note to tain useless/trash or should it be held onto? it doesn't seem like it has anything to do with the quest (from what i read)

looks like you just talk to tain, kill the giant, hand tain the elixer?

Useless, just say "I will help" or whatever his keyword is *i think that's right*

As a small side tip, if you fail to defend him or don't kill the giants before he depop's don't worry too much, just kill the named giant and loot the "frozen elixir" anyway. Next time Tain spawns you can say "I will help" to make him stand up and immediatly hand him the elixir, and then kill the named giant at your leisure to get another frozen elixir

This.

Oh, and the named giant is level 50, at least he was last time I did this. I think the Wiki reports a lower level.