In my school years I used to play a casual format with my friends we called „King and Flanks“ (german „König und Flanken“). Here is what I remember rule-wise:

You have two teams of three players each, with one king per team and two flanks (left and right). The each flank can only attack their opposing flank and once that player was dead the enemy king. The king can “send” their creatures through their flanks and can attack with the same abilities as either flank. The players have separate life totals, but share a turn (i.e. have to declare attackers at the same time).

What I am unsure about is how targeting spells and abilities work. Limiting the restrictions to attacking creatures seems unbalanced to me.

The format was a lot of fun, since slow decks can really shine as kings. We never build decks specifically for this format, this might have broken it.

Has anyone ever heard of such a format? What do you think the targeting limitations should be? Can someone point me to a source of this? I could not find anything on the internet.