Boss Bot is a gigantic slime enemy that appears in Zelda II: The Adventure of Link.
When multiple Bots merge together, they form one giant creature called Boss Bot. Only a few Boss Bots can be found, and they all reside in the Great Palace. They remain invisible until Link walks under certain recesses where they hide. Once on the ground, they jump around to attack Link in the same pattern that standard Bots use.
If Link is fast enough, he can use an Upward Thrust to attack Boss Bots when they drop on him. After taking damage, they split apart into several Bots, which are stronger than the normal ones. If Link casts Spell on these strong Bots, they are transformed into the weaker variety that only require one hit to kill, but still give 10 experience points.