D&D 5E How do I make a challenging investigation for a high level cleric?

[Shadowdweller00]

I don't suppose it has occurred to several possible individuals here that the meaning of "familiar" in the Find the Path spell has been left intentionally and deliberately vague. As far as I'm concerned as a 6th level spell with the prohibitive requirement of long-term concentration, the spell needs to be more powerful than "Show me how to find some place I've already been to."; but for reasons of preserving plot also more limited than "Show me the hiding place of the hobgoblin mastermind that I theorize exists": and perhaps even more limited than "Show me the lair of the dragon that just attacked me (which I've never previously seen or learned of)."

The answer (in games I run) is to treat a written or spoken description, or physical or mental image, of the location as "familiar". A caster could thus conceivably find a place depicted in a painting, described by a witness to some event or written in a book, seen through Scrying, or picked up from a Read Thoughts effect.

 

[devincutler]

Situations where Drawmij's summoning is actually the best spell to use take a fair bit of contrivance. Both the scenarios you list have lower level solutions that don't cost thousands of gold.

Lower level solutions if the security is also lower level. A lot of anti-teleportation effects in 5e affect only creatures (see Hallow, for example). While it doesn't explicitly state that Instant Summons is a teleport, even if it were, most of these anti-teleport measures would fail. I can easily see a temple with Hallow in place in its library to stop people from teleporting out. Someone wants to steal a rare book. They read it, mark it, give the boo back to the librarian, subject themselves to search (for a book) at the exit, and go to the inn or home where they then activate the summons and BAM! Have the book.

The spell states that the object gets an invisible mark, and the sapphire has the name of the object invisibly scribed on it. Detect invisible would have to be the number one go to spell of magical security. There is also an active, dispellable magical effect on both. If that's not detectable with detect magic, then nothing is.

Interesting point on the dispellability. That does imply it radiates magic. I don't buy the detect invisible because if the gem is in your pocket or set into your tiara then there will be nothing to detect (in the latter case assuming the invisible mark is facing the setting of the gem). In any event, a simple Nondetection spell stops that and the detect magic. And a physical search turns up nothing because....you don't have the object you intend to smuggle out!

It lets you escape any maze. That seems good to me, even before you use it to mark every way out of the underdark or use it to find which way does not lead you back to the entrance to the dungeon.

Every way out? It marks the shortest path doesn't it.

 

[Saeviomagy]

Regardless, Drawmij's has a narrow use case and it's far from a sure thing even then.

Every way out? It marks the shortest path doesn't it.

At every junction it tells you which way is the quickest route to your destination. You don't have to take the route it suggests.