Demons & Devils Gating in Others

[Juju EyeBall]

That would destroy the fun flavor of succubi being able to gate in demon princes (unless you specifically made them an exception).

Woah, hey. This ain't Carcosa.

[grodog]

Another way to do this, although not BTB, is to adjust the monster's description to only allow gating in of lesser creatures. [snip] This way, even if the monster gated in a new combatant the power creep is a downward spiral and contained.

That would destroy the fun flavor of succubi being able to gate in demon princes (unless you specifically made them an exception).

Like removing energy draining, I think that the ability for a monster to summon more of its kind---lesser minions, peers, as well as sometimes the big guns---is part of the way to keep experienced players and PCs on their toes, and to keep that threat of death and loss front-and-center in the encounters matrices. Demons and devils (like energy draining undead) help to keep the game interesting, and challenging at all levels of play. Even a very high level group of PCs has to worry about whether the succubus they failed their Turn roll on will gate in Demogorgon (and, of course, those rarified moments of gaming that we all love to remember and recount years later occur when just those rare instances become stark and sometimes horrifying reality).

"Real" demons and devils don't begin to appear on the DMG encounter tables until Monster Levels 6 and 7 (page 178)*, and since such monsters aren't generally encountered until Dungeon Levels 8 or deeper (though they can potentially appear in as high as 4th level dungeons--see DUNGEON RANDOM MONSTER LEVEL DETERMINATION MATRIX on page 174), they are available as encounters to help prevent that certain level of jadedness and "we're ready for anything" attitude that successful PCs and players will likely have by the time that they're delving that deep into a dungeon. Those PCs will have mowed through hyrdas, lycanthropes, giant snakes, dragons, giant spiders, cockatrices, basilisks, and carrion crawlers (among many others) by this time, and demons and devils significantly step up the level of challenge to such PCs. Not only through their gating abilities, but also their at-will magical powers, magic resistance, resistance to normal and low-level magical weapons, and (in many cases) high intelligence.

* It is worth noting, however, that manes are Level 1 monsters, and lemures Level 2, which suggests that PCs "should" at least be somewhat familiar with these "least" outer planar creatures early on in their careers. Quasits and imps are Monster Level 5 encounters---and higher, when you attach them to evil MUs and clerics as familiars.