Morph is a modification for Quake made by Jeff Epler. This modification was inspired by and expands upon the concept of THE FIEND MOD. While the aforementioned modification just let the player become a Fiend, this modification allows the player to choose between eight different Monsters. All Monsters are given behavior like their normal counterparts and will be colored slightly to show their team/player colors. The player will appear to be the Monster and will give death messages identical to the Monster the player currently is. Monsters cannot pick up items on the map, meaning Powerups (beyond health pickups like 25 Health), Ammo, and Weapons cannot be touched. Player movement speed is unaffected by the modification. Note no new meshes exist, meaning the player that is the Monster will only see the ranged attacks, melee attacks are entirely invisible to the player controlling the Monster.
Impulse 90 allows the player to become a human, useful for switching back from a Monster, and is the default value for all players. Impulse 91 switches the player to a Zombie. The Zombie is limited to throwing slow projectiles that can easily be prevented from being thrown by being constantly attacked. The Zombie also cannot jump, which means it is highly limited in mobility. However, the Zombie is invulnerable to all normal attacks, staying comfortably at 75 health and falling down/regenerating at 70 health. This means the Zombie never needs to worry about resource collection and can endure a lot of risks. Note however that the Zombie shall Gib if exposed to explosions.
Impulse 92 switches the player to a Vore. Note that the Vore has a large bounding box that might make it impossible to navigate certain maps. Note also that the Vore's sole attack, the homing pod, does not follow any Monster that isn't another player (it needs to be shot directly at them, like a Rocket Launcher). The Vore also gets a massive bonus to their health, holding 300 at a single time.
Impulse 93 switches the player to a Scrag. Scrags can fly around the map if the jump key is held down, or just hover above the ground if no button is pressed. Scrags have 200 health and shoot fast but weak projectiles at their opponents.
Impulse 94 lets the player be a Death Knight. 1 on the number keys is used for melee sword strikes, while all other numbers let the Death Knight use his ranged attack of a spread of fireballs. He has a health of 250.
Impulse 95 lets the player be a Shambler. Like a Death Knight, 1 can be used for strong melee attacks, while all other keys lets the Shambler perform his lightning attack (which must be aimed at foes). Note that the Shambler has a giant bounding box, meaning it is very possible for the player to reach areas where they cannot pass as this Monster due to the difference in hitbox size with Ranger. Furthermore, the hitbox itself is smaller than normal, meaning Weapons can possibly go right through a Shambler (such as a Grenade Launcher or Vore pod passing right through a Shambler). This bug seems to affect regular Shamblers as well. Shamblers have 400 health.
Impulse 96 lets the player be a Fiend, which should play mechanically similar to the one found in THE FIEND MOD. The Fiend has a health of 500 and relies mostly on jumping into foes to injure them. The Fiend can also claw at opponents if they happen to get too close.
Impulse 97 lets the player be an Ogre. 1 can be used to attack with the chainsaw, while all other keys allow the player to fire grenades very similar to the player's (these can gib Zombies, unlike actual Ogres'). The grenades fire at a very slow rate. The Ogre has a health of 275.
- An similiar concept was later used for the Monster Match modification. However instead of impulses Weapons are replaced with Monster morph collectibles which players can collect and turn into their respective monsters.