Explodo's Level Up Ability works in a way that is a cross between Boulder Ramp and Bottomless Pit. It is recommended to have this ability activated as soon as possible, but definitely before the Epic Heroes come to town, as Explodo's Ability is definitely a big help when taking them down.
While Explodo's ability seems powerful, it definitely has quite a few drawbacks. The random damage output of the ability can mean success, or a waste of a Room. The nature of the Ability does pair well with Recycling Center, however, and can mean that this Boss can have plenty of potential ammo to use during gameplay.
It is also recommended to plan ahead and build as many room stacks as possible, as Explodo can leave a dungeon feeling rather small if the player is not properly prepared.
Below is an excerpt from the Boss Monster: The Video Game update talking about Explodo in terms of gameplay, and his character:
ABOUT EXPLODO: Deep within the dungeons of Arcadia, factories churn out explosive Bom-Boys at a steady rate. Even a run-of-the-mill Bom-Boy is a threat to most Heroes, but Explodo is the cream of the crop. Unpredictable, too hot to handle and too cold to hold, Explodo is ready to freak out, bust through the walls, and take down some Heroes! Ohhh yeaaaah!
GAMEPLAY: Mechanically, Explodo is one of two cards in digital Boss Monster that can deal a random amount of damage to a hero. The effect is uncertain and the cost is high – you have to destroy a Room every time you use his ability – but it’s worth a gamble when Epic Heroes are coming your way.