E2M1: The Crater (Heretic)

E2M1: The Crater is the first level in the Hell's Maw episode of Heretic.

Walkthrough
You begin facing a wall of hardened lava. Walk around this wall to find yourself in an outdoor area facing three passages. Only the middle one is open, so go through it. At the end of the passage, collect the Ethereal Crossbow and pull the switch. Backtrack and head through the second passage which is now open. After having met a new enemy - the weredragon - and proceeded further, you will find yourself in a cave with a pool of lava at one side. Drop into the lava and hurry around the central rock to find the yellow key there in a teleporter. Grab it and you will reappear near the start of the level. Head through the yellow door into another cave. The green key is on a rock at the northern end of the cave. Hurry across the lava to grab it, then go back up the stairs. Cross the bridge and use the green key to open the exit.

Secrets

 * 1) In the northeast of the weredragon cave, there is a wall that appears lighter.  Open it to find a secret chamber containing a Silver Shield, a Tome of Power and a Crystal Geode along with some smaller ammunition bonuses. There are also some gargoyles guarding the goodies.
 * 2) After you cross the bridge towards the green door, backtrack and find a passage opened into the weredragon cave.  Go through and you will find a secret chamber opened nearby, where you can collect bonuses, including a Bag of Holding and a new weapon, the Hellstaff.

No credit is given for finding this secret:
 * 1) Near the green key, there is a wall that has some brown stone at the bottom.  This is a secret door concealing yet another new item, a Mystic Urn. The second one of the two Crystal Geodes can also be discovered here.