Proactive Bosses will use every dirty trick they know to slow down, harass, or even outright kill the player off well before the real battle officially starts; they will personally break bridges or set off traps until they're left with no choice but to fight.
Compare "Get Back Here!" Boss (this only happens during the battle) and Final Boss Preview when this is done over the course of an entire game (as opposed to a single dungeon). If a boss actually battles you several times in a row, it can be a Recurring Bossnote , Sequential Bossnote , or Cowardly Bossnote , depending on the context.
- In the Buzz Lightyear Super NES game depicted in Toy Story 2, Emperor Zurg tries to kill Buzz with a Smashing Hallway Trap before Buzz reaches him.
- Dungeons & Dragons: Count Strahd von Zarovich from the classic I6 Ravenloft module was one of the first (if not the first) such bosses in D&D, showing up in different corners of his eponymous castle to manipulate the heroes (if not to try killing them outright). The module was highly praised at the time for its intelligent and proactive villain, as most D&D modules until then (1983) had been little more than straightforward Dungeon Crawls where all encounters were either nailed to their rooms or completely random.
- In the Pathfinder adventure Rasputin Must Die, the titular mad monk uses Astral Projection magic to harass the heroes as they attempt to gain access to his extraplanar sanctum.
- Golden Sun: The Lost Age: A rare case in that it's not done to the player: Agatio and Karst trigger a trap that causes the previous game's PCs Garet and Mia to fall down a hole, leaving only Isaac and Ivan to fight. They're defeated by the time you reach them (no matter how high you leveled them up previously), and the true boss fight begins.
- Golden Sun: Dark Dawn: On entering the Phantasmal Bog, the first thing you'll notice is the giant purple-aura'ed salamander glaring at you from the water. The second is when it tries to drown you by crushing the part of the stepping stone you're standing on. The entire point of the dungeon is to get to a different area in the same room where there's enough space to fight it on land.
- Twilight Princess:
- The City in the Sky is guarded by a giant wyvern, who at one point smashes through a stone bridge leading further inside (fortunately, there are alternate methods of crossing involving hookshots and helicopter plants). The actual battle takes place on the highest rooftop of the city.
- While the Skull Kid periodically sends puppet fighters after you, he also inverts the trope by opening up other sections of the dungeon when he goes through them.
- Mega Man X:
- Mega Man X4: Jet Stingray attacks you halfway through his stage.
- Mega Man X6 has Illumina, who attacks you throughout Infinity Mijinion's stage.
- Mega Man X8: Gigavolt Man-o-war's level is a big chase against him, with you on your Ride Chaser and him flying around the city area, occasionally leaving bomb traps or exploiting tight turns to slow you down. Shoot him enough with your Ride Chaser and he'll go down to a platform, initiating the proper boss battle.
- In Mega Man 11, three pile driver robots called the "Impact Brothers" charge you throughout Impact Man's stage. Once you reach the end of the stage, the Impact Brothers combine into Impact Man. This is the first time a Robot Master doesn't even wait until the Boss Room to screw with the Blue Bomber.
- Traditionally, Bowser from the Super Mario Bros. series spits fireballs at you from afar in the levels you encounter him in before the actual fight.
- Before fighting Gary in Bully, Jimmy Hopkins is forced to give chase up to the roof of Bullworth Academy. All the while, Gary throws bricks at him when crossing thin scaffolding, and tries to tip carts filled with cinderblocks on top of him when he climbs up ladders.
- God of War II: The game begins with the Colossus of Rhodes coming to life and attacking Kratos. The Colossus chases him throughout the level, becoming an obstacle or a hazard at points when Kratos is navigating the level or fighting other enemies. The level ends with Kratos and the Colossus finally squaring off, where Kratos defeats it.
- In Rayman (1995), Mr. Sax, Mr. Stone, and Mr. Dark all attack you early into their respective areas.
- Played With by the Giant Spider Mactans in Kingdom Rush Origins. Throughout the penultimate and final stages, she harasses you by webbing your towers and spawning spider minions and covering the path in webbing. At the end of the final stage, she's never directly fought as herself since she and Malicia fuse together to become the Spider Goddess.