KGB,
but my assassin should have basic UL 7, not 5.
For the same exp with same intelligence, I would need to get get two neutral cities with 2 and 3 turns defenders. Even if some were around, it would take much more time (and I would risk loosing some units). Now this experience is given me for free - I do not risk anything. Very easy to level up heroes this way
The item shows what's exactly in the ruin - allies, amount of gold, kind of item and guardians.
It was turn 11 when I found the item. I had 3 L3 heroes and 1 L2 at the moment. None of my L3 ones has raised his basic UL and wasn't meant to search any ruins except for L1, and even them with couple of scouts. Now I can pull valuable allies out from any ruin with any of them.
It seems game breaking for me, even if I didn't know what kind of allies is there. Still it would level up my heroes very quickly with absolutely no risk of anything, and I would get some very strong units (even two demons are very good on mostly non-flyers map). Normally, in the similar stage of the game, I search L2 ruins (usually with supporting units and not with every L2 hero). I could probably search some L3 if I trained some heroes that way and built enough supporting units, but usually I invest primary to expanding. Also, if I wanted to get such allies with hero offer, I would need a lot of gold for that. Comparing to some 400 gold or other L1 items, this one is miles ahead.
I think it would be still very valuable, if you had to fight undead for allies. It would still make it much easier, since you would know that you don't need as much UL for ruin you want to search as if you could expect some heavy guardians there and you knew what kind of award to expect.
Chazar,
it has limited power to view range of all of your units. At the moment I found it, it meant two L3 and at least 4 L2 ruins I had immediatly around my troops and cities (this includes all of ruins my heroes can quickly reach). With each new turn, I can check more. I could quickly check all the map which isn't under heavy enemy's control.
So I think only limiting the item to view of his wearer would make it comparable to other L1 items.