I'm not entirely sure what kind of feudal system encourages knights to mount gigantic birds and whizz around inside a volcano, but it's precisely the kind of bizarre tournament of which arcade dreams are made.
Sadly, the original cabinet of 1982 didn't include a pantomime-style ostrich body to sit inside while playing--but the addictive gameplay was probably enough to keep you (and a pile of change) there anyway.
As one of the ornithologically-based participants in this strange contest, it's up to the player to hop between platforms and fend off waves of increasingly vicious high-flyers with his trusty lance. Striking an opponent from above results in glorious victory (and the chance to snatch a dropped egg to prevent more foes appearing), colliding from below is a ticket to failure. Simple ... but oh so tricky.