Well, how'd YOU defend the GATES?

[DaggerPen]

I think ChillerInstinct, and certainly I was in an earlier post, is working from the basis that at some point in the past the gates were created - the reasons they were made as gates and not as walls is unfathomable, lost to the mists of time. It is logical to assume that those who created the gates knew about a set of circumstances which may require the gates to be opened, and therefore built in that possibility. Those coming afterwards can only work on the knowledge that what is behind the gates can destroy the world and therefore fortify them as much as possible - preferably with defences that would still be up and running were you to die / get killed - but still leave open the possibility of opening the gates based on an unknown, but existing requirement.

We call these the "known unknowns" - things we don't know, but that we know we don't know. In project management the approach is to take these into account and build in a certain amount of flexibility for a time when the unknowns may become knowns.

Which I believe is DaggerPen's point, in the event that the known unknown occurs and ChillerInstinct needs to access the gate the protections they have on accessing it will mean that they cannot unless they get multiple groups of multiple alignment people working together and willing to sacrifice themselves - unless they have a backdoor, which than could be exploited by others (Dorukan's backdoor was the bypass for pure of heart, ChillerInstinct would likely need a backdoor for the backdoor if they wanted to access the Gate).

Frankly if you are going the route they laid out I imagine most people trying to assault your gate will merely bypass the protections via dispel magic, break enchantment, mordenkainen's disjunction or use magic device combined with disarming device (to avoid the fatal elements).

Dancrilis partially got it, but I think you're sticking a bit on them being called "Gates." The fact that they're "Gates is irrelevant to my point. The Gate is not the door in my extended metaphor - the sigil is the door, and the conditions used to pass it are the key. Using byzantine conditions that no one's really meant to meet is the thing with the mold.

In fact, let's pretend for a second that they're not Gates at all - they're just unidentified MacGuffins you have to guard for unknown and irrelevant reasons. Now, say someone comes along with the proposed sigil plan again. My question is still "Why on earth would that be the vulnerability in your sigil?" You put bypasses like "lets only the pure of heart through" in order to allow access - if you're trying to deny anyone access to the MacGuffin whatsoever, leaving a hole, no matter how Byzantine, is a non-optimal solution compared to "throw that exact same type of magic into a ward that just keeps anyone out". Meanwhile, if your goal were instead "keep most people out but allow emergency access", your sigil conditions are nigh useless, because bypassing them takes ages.

Could you just dispel the sigil if you needed in? Absolutely! As dancrilis alluded to, sigils are still vulnerable to brute force attacks like dispelling, etc. What else is in the exact same situation? A ward that just zaps everyone who tries to get in - except that one can't also be bypassed by meeting the obscure conditions.

Rule of thumb - don't build a backdoor into your defenses unless it's meant to be used. A condition literally no one is actually supposed to meet is a condition you should leave out.