Notes about Heretic and how Heretic things work!
This probably isn't everyone but I'll give credit to Not Jabba, Gez, and ETTiNGRiNDER for their posts on Heretic threads. Thank you to all the Heretic gamers whose notes I've copied down to help put this together! Ahem..
1. Heretic The Way Raven Did
All levels follow the yellow-green-blue key order. Sequentially it is always yellow, then yellow to green, then yellow to green to blue.
All locked doors are flanked with orb statues
All wooden panel doors are free to open. All steel panel doors are locked in some way.
Switches are always recessed the same way (unless you must use a linedef's lower edge, but do it rarely)
Only use one kind of switch for miscellaneous activations, and the other kind of switch only for exits.
Exit doors also have their own specific design and are mandatory.
All teleporters have red glitters on top of a specially textured pad.
All walk-over exits have blue glitters (on top of a specially textured pad) and tend to appear in episodes 2 and up.
2. Heretic Gameplay
Heretic is more exploration minded akin to Doom 1 and it wants you to manage your inventory and make extensive use of it, which is Heretic's unique mechanic. Every item has its place and something that makes it useful.
You can still make tight and action-packed encounters in Heretic. Embrace what you are working with but take care to not be monotonous. In tandem with the inventory items you can create multitudes of strategies in how to tackle various encounters and establish set pieces.
3. Heretic Artifacts (inventory items)
Heretic's unique inventory can complicate mapping as certain items can break a map with the non-linearity they allow.
-Morph Ovum: Good for crowd control when overwhelmed. Does not work against Iron Liches, Maulotaurs, D'Sparil, and his Chaos Serpent. The health of a chicken always becomes the same so it's better used on uninjured enemies lest you waste damage. An early weapon of the game.
-Shadowsphere: Cannot be hit by undead warrior axes, iron lich tornados cannot target you and iron lich ice balls (before it splinters) cannot hit you.
-Mystic Urn & Quartz Flask: reinforces reliance on inventory management to survive! If you want to tank a lot of damage then you'll have to stock up on these.
-Time Bomb of The Ancients: you can make a bomb wherever you are! Defend chokepoints or simply plant an explosive amidst a crowd and watch the show. An early weapon of the game.
-Tome of Power: If you've played Heretic you already know how much it rules! For 40 seconds all of your attacks are much more devastating.
-Ring of Invulnerability: Very strong and the power to be lazy whenever you want. Glorified radiation suit? For 30 seconds you are invulnerable to all damage. Feel free to drop all the bombs and get in all the monster faces as you please.
-Torch: Brightens the map, but flickers! Use before entering a foreboding darkness.
-Chaos Device: Lets you teleport back to the start of the map whenever you wish. You can escape inescapable death pits, and have shortcut back to the start. Don't let your maps be broken by it!
-Wings of Wrath: Grants you the ability to fly! Reach the next highest floor from down below and the next lowest ceiling from up above. Reach secret areas that would be unaccessible otherwise, scale tall towers, or simply have an alternative way of reaching areas!
4. Heretic Ghosts
Utilize ghost features, including physical vs magical dmg types. Heretic has a rare advantage to Doom in creating projectile-Hells through the use of undead warriors in the back, firing their axes through ghosted nitrogolems/undead warriors.
Packs of ghost warriors are efficient turrets -- since their projectiles go through their fellow ghosts, they will not block the attacks of the ghost warriors behind them. Likewise, a pack of ghost warriors can efficiently be shielded by ghost golems or ghost nitrogolems.
5. More Uniquely Heretic
Heretic does not have infinite height. There is over/under in the game.
You can physical push the gas pods by moving into them.
Gas pods can be carried by moving sector types, telefrag by exploding on top of something, and can be stacked one on top of another. Knowing this you can create some clever puzzles and fiendish traps.. maybe even some kind of scripts?
Certain projectiles move along the sector's WIND current.
You cannot leech health from the gas pods (Gauntlets powered up mode)
Phoenix Rod's powered up flamethrower consumes only the 1 ammo upon firing.
Dragon Claw's powered up mode can hit enemies you don't see around corners.
Firemace projectile speed is based on your own. The powered up mode's projectiles can consistently bounce in the same pattern.
The Wand's powered up mode is very good at stunning enemies in close quarters, firing 7 individual shots at once.
Have fun gibbing packs of gargoyles with the Phoenix Rod!