When the Level Timer expires, any heroes who have died during the creep wave phase of the level will be revived over 15 seconds.  Shortly thereafter, the Level Boss will arrive.

Each level has a different boss mechanic.  Some will arrive more quickly than others, sometimes the creep waves will cease, sometimes there will be special creeps for the boss fight phase, other times creep waves will continue normally throughout the boss fight.  The boss itself will always have some type of special ability; early levels will have fairly simple boss fights where the abilities can generally be overlooked.  Beginning at around Level 4, it starts to become very important to strategically approach Level Bosses, and take quick notice of any tips provided for the Boss Fight phase.  Note: Level 10 and Level 16 are exclusively Boss Levels – there will be no creep waves during these levels; all you have to do is kill the boss.

Once you kill the Boss of the level, the game immediately recognizes that you have completed that level, any dead heroes will be revived, all remaining bad guys will be destroyed, you will be given your gold reward for that level, and you will be granted a Level Up!  Leveling up increases your hero’s base attributes, and grants the hero a single skill point that can be spent on a new ability or increasing the rank of an already purchased ability.

Each boss you kill in Defend the Basement drops at least one item that can increase the effectiveness of your hero.  Some bosses will drop multiple items, and some will drop one item for each hero in the game.  Usually it is up to the team to strategically distribute these item rewards cooperatively, with the exception being the latter mentioned case where bosses drop an equal number of valuable shards or power ups that are traded to a vendor named Sheldon (the hermit crab near the Tavern of the Gods) for a unique type of item.

Many of the items obtainable in Defend the Basement can be combined with other items, becoming more powerful and saving inventory space.  The Customs Shop near the Tavern of the Gods contains all of the available recipes for combining items; most are available at a small cost.  For more detailed information about items, see the Items Section.