[Z] killing friendly uniques

[aurgathor]

I wonder if it's worth killing friendly uniques, specifically Gandalf the Grey.

What do people usually do?

In the current level he summoned his friends and cleaned out most of a greater vault and I could just walk in and pick-up 4 artifacts without any effort, but it's usually a big mess, and those A's pick-up everything else. On another level, there were other summoners and I could barely escape alive.

TIA