Course No.20 is the first course of Stove Canyon in Wario Land: Super Mario Land 3. In this level, Wario must run away from a wave of lava that chases him from the left while overcoming many obstacles along the way. Touching the lava wave results in Wario instantly losing a life.
The lava wave begins to chase Wario as soon as he enters the level. After jumping over a small hill with a Pirate Goom, Wario must break his way through a small passage; if he is Small Wario, he can walk through the gap at the top. Wario then climbs up a ladder to another Pirate Goom and a cliff overlooking lower ground with a small lava pit to the left of it and several coins, though after he jumps down, Wario must break through the blocks to reach higher ground and proceed further. Next, Wario crosses a bridge that leads down to another bridge, which leads to the left towards the lava wave (if Wario isn't fast enough at this point, he can potentially run into the lava), then down to lower ground where Wario can then continue heading right. The path then splits into two: the top path is occupied by Pirate Gooms, while the bottom path is a passage filled with coins walled up by breakable blocks. After the paths converge, there is a block that contains a Star, which Wario must use to plow through the next area, a zigzagging passageway blocked by Pirate Gooms where Wario must climb up and down multiple ladders to proceed. At the end, Wario finds the door leading to the final room blocked off by more breakable blocks. In this wooden room, a ladder leads down to the goal door (already open) guarded by a Guragura.
When Wario runs across the bridge towards the left, if he is far enough ahead of the lava wave, he can hit the block to the left of the bridge to obtain a key. Wario must carry it all the way to the final room, meaning he can only take the upper path after the bridges to proceed, as he cannot break the blocks on the lower path in time while carrying the key. Once in the wooden room, Wario must climb up the ladder to find the treasure room door. The treasure Wario obtains is an orb worth 5,000 coins.