Tag 667

Tag 667, closely related to tag 666, is used on Doom II's MAP07 in conjunction with the Arachnotron. This is the relevant code (from p_enemy.c, lines 1722-1727 in the Doom source code release):

if (mo->type == MT_BABY) {  junk.tag = 667; EV_DoFloor(&junk,raiseToTexture); return; }

When the last Arachnotron dies, any sectors tagged with the number 667 are raised up by the height of the first sidedef's lower texture. If the first sidedef does not have a lower texture, the second sidedef is used.

Tag 667 is also used in Strife. Killing all Crusaders on any map will cause all sectors tagged 667 to lower their floors to the lowest surrounding floor. This effect is used in MAP02: Town in the demo version, and in MAP09: Castle: Programmer's Keep in the registered version. At least one player must currently be alive for this to happen.

Bugs
Sometimes, if the last two Arachnotrons on MAP07: Dead Simple are killed such that the last one dies before the death animation for the first one has finished, the step to the exit switch rises twice, placing it too high for the player to step onto. The level can still be completed by straferunning to the step from one of the square metal platforms, if lowered.

This bug occurs because a monster is considered dead to the source code at the beginning of its death sequence, but A_BossDeath is triggered at the end. Therefore, there is a short window where an Arachnotron at the end of its death sequence could erroneously be considered the last Arachnotron if the 'real' last Arachnotron is still in the middle of its death sequence.

In addition, if the level is played with respawning monsters toggled on (either through using a command line argument or playing on Nightmare! difficulty,) killing every Arachnotron that respawns after the whole group is killed for the first time will cause the step to rise up another time, resulting in the same effect. Unlike the above, this can be done repeatedly, which will eventually cause the step to rise up to the sky. The inner sides of the step are untextured; if the player raises the step high enough in this fashion while standing on the exit platform, they will be able to see through the newly created walls, providing a view of the courtyard while remaining hidden from the enemy.

Demo files

 * v1.666/PrBoom demo (file info) showing the double-rising bug on MAP07: Dead Simple.
 * Doom95/v1.9 demo (file info) showing the double-rising bug on MAP07: Dead Simple.
 * Doom 2 Bug - Can't escape Map07 'Dead Simple' en YouTube.