Bacura appears as an enemy in Smash Run. They are invincible obstacles which appear in groups. These indestructible spinning boards can reflect projectiles. Touching one deals 4% damage and cause a meteor smash effect on the fighter.
These panels are enemies from the arcade game Xevious. In this game, multiple panes will appear on-screen at once, dropping down on fighters from above and passing through the torrain. Like in Xevious, they can't be defeated, so all that's left to do is dodge around them or get out of there in a hurry!