Storm, nearly all empty crates/boxes/chests/barrels in the classic Tram/Fel dungeons are like that.
They spawn empty, then once a LP pops them once, they will keep refilling with normal armor & weapons, bones & body parts, and magery scrolls level 1-8 (and occasionally a blank scroll, much like an air ele), as long as someone keeps emptying out all the contents (and it occasionally re-locks). If the respawn timer passes, and no one picks it and empties it out, it will return to an empty state on the next server maintenance.
I used to do the crates in the alcove between the main bowl of Destard and the water eles in the SE for level 8 scrolls, as well as using the 3 random chest spawns in the same area for LP gains.
Cerwin Vega: Here's a quick rundown of the best scroll sources (*also includes necro scrolls of equivalent power)
Level 1-3*: Orc Mages, Rat Mages, Imps (includes 10 of the 17 Necro spell scrolls). will sometimes have a blank scroll instead of a spell scroll.
Level 1-4: NPC Mages in shops. Will randomly have only level 1, levels 1-2, levels 1-3 or levels 1-4. Be sure to check every mage in the shop, as they are usually different from each other. Only sell mage scrolls.
Level 5-7*(and 6 of the 17 necro spells): Liches, Daemons, gargoyles, Treasure Chests from T-maps and SOS.
1 Level 1-3* & 1 level 4-7*: Air Elementals (As noted above, sometimes the lower level scroll will be a blank, instead of for a spell).
See my earlier post for the list of level 8s (and the necro spell Vampiric Embrace, which is level 8 equivalent).
You should be able to go through your book by the level pages at the beginning and see exactly which levels are missing spells.