I'm interested in trying to use the AD&D spells BTB as much as possible with my group, however I'm having a hard time wrapping my head around the 4th level M-U spell Dig and I haven't been able to find a clear answer to any of these questions online.
I'd be interested if there are any official answers to these from back in the day and/or how you guys rule on this spell in your own games.
So here are my questions:
Total Duration: Duration is listed as 1 round/level, but is that limited to a maximum of the area of effect (which is listed as a 5’ cube per level of the magic-user)? Or can the MU excavate the area of effect every round? In other words, can a 7th level MU excavate 35' down per round for a total of 7 rounds, or is the maximum total excavation 35' and then the spell ceases once that is reached whether the max duration has been reached or not? I'm asking this first, because if the spell ends after the maximum area of effect is reached, then a lot of the other questions become easier/less of an issue.
Rate of excavation: "A dig spell enables the caster to excavate 125 cubic feet of earth, sand, or mud per round" but again I'm assuming this is just the maximum rate of excavation right (for a 25th level MU), but a 7th level caster would only be able to do a maximum of 35' in one round, right?
Range: So the range being only 30' means that in practice most MUs of level 7th+ will be able to dig several similar sized holes over the course of the spell, instead of continuing to dig a single very deep hole unless other magic is used to get them closer to the bottom of the hole they dug in the previous round? (which would be a risky proposition in any case if you consider the risk of collapse)
Chance of collapse: It says in the spell description that "If the magic-user continues downward beyond 5’, there is a chance that the pit will collapse: 15%/additional 5’ in depth in earth, 35%/additional 5’ depth in sand, and 55%/additional 5’ depth in mud." Is the chance of collapse cumulative or does it stay at that same percentile chance for every further 5' of depth? When is the chance of collapse checked: every 5' or once only at the end of the round?
Effects of a collapse: When a hole collapses, does it collapse from the surface all the way down or at a certain intermediate level? Is a creature who has fallen in automatically buried alive or is there a saving throw allowed? Does a creature that is burried by the collapse take damage? How many rounds until it suffocates? Can it break out somehow or is it completely trapped?
Large creatures: the spell mentions that "Any creature caught in the center of a pit just dug will always fall in." However, given that the hole is 5' per side, I would assume that this would not apply to large creatures like dragons, etc..
Original inspiration: Finally, in thinking about all the above questions, I'm curious about whether anyone knows if the Dig spell was modeled on something from a story or novel? I'm asking because it might help me better understand the original intent behind Dig. With "Move Earth", it's very clear that the main function is to modify the terrain in preparation for a battle or in order to build foundations, etc... and not to be used in a direct combat setting.
P.S. I did a google search for "wile e coyote fall into hole" to see if I could get a funny picture to link to this post and instead this came up as one of the top hits:
[Edited because for some reason points 2 and 4 got cut short, which I have now hopefully fixed]