With Bards portals, if you have vision of a portal when its created, then lose vision of it, you can still see the portal, and more importantly, you can see all the people that go through the portal, along with their health, level, items, ect. exactly as if you had vision of them.
What happened: I was playing a game as Galio, was killed in a bush by people going through a portal to me, then a few seconds after several other people went through the portal and I could see their health and other stats even though I had no vision of either side of the portal. I assume this only happens if you have vision of the portals creation but I have not tested it yet as I cannot go into custom games due to server overflow.
Steps to reproduce (I think):
1. Have vision of a portal being created by Bard, then lose it probably in any way, either by dying, pink ward being destroyed, a ward being Oracle'd or timing out, or simply walking away.
2. Have enemies walk through the portal with no vision of any part of the portal, and you will see all the people going through the portal.