I think I saw this happen once back in the last Emrakul’s Corruption where an eldrazi played against me didn’t ingest any gems, and I just figured maybe if the targeted gems happened to already be supports/activated/etc that it just wouldn’t happen. But just now in a TG match the opponent played an Oblivion Sower which ingests 10 on entry, and on an almost empty board nothing was ingested.
@stikxs Karn is colorless, ingest will not convert.
Also, you need permission from your opponent to post their username on the forums …
^
This is a quirk if Karn being colorless. Not a bug, but would be nice if they adjusted the mechanic to ingest random gems when facing him.