What happens when a creature falls on player-improvised spikes?

Question

I'm new to D&D 4e. What happens when a creature falls on some spikes or on the blade of a weapon from 10 feet or higher?

I've encountered situations where, for example, one character lifts an enemy 20 feet into the air, and someone else puts something deadly under the creature which it will fall on. How should I calculate the damage from that kind of fall?

For background: they can lift it because of a telekinetic Psion with the Level 2 utility spell Telekinetic Lift. With that spell he can move a creature of 400lbs or less 3 squares (even into the air) but he also has orb expertise so he can lift it 4 squares high and cancel the effect for a free action.

Logically, if he cancels the effect while the creature is in the air, it will fall. If someone had put an object (like a spike or a weapon) underneath the falling creature (e.g. the psion used Far Hand with as a minor action), the creature would fall on the object and do normal falling damage plus some extra damage from the object.

So from the situation I explained, how do I calculate the extra damage caused by the spike or the weapon?

Answer 1

Unless you want it to just cause automatic death, the answer you're looking for is on Page 42 of the DMG. If you're consulting that page for other purposes, please note the errata.

First, determine whether this situation is easily repeated ("normal damage") or something that could only be set up once an encounter or so ("limited damage"). Next, determine whether you think this situation counts as "low," "medium," or "high" damage.

Now reference the table on Page 42 by your PCs' level to determine what damage roll you should make.

This is the page the DM should consult whenever a situation comes up that requires a DC or damage expression that isn't covered by other rules.

Note that I'm assuming you're using the power correctly: only on a helpless enemy. Even if you're not, the answer applies to various other situations such as a forced teleport.

Answer 2

It really sucks to be this Psion's "ally". Treat this betrayal as a normal readied attack from the weapon and player involved, or as a trap, depending on how much bracing is available.

First, a clarification. This question should never come up in play, because Telekinetic Lift's target is:

Target: One ally, helpless enemy, or object that weighs 400 pounds or less and isn’t carried by another creature

However, it could happen, so long as it wasn't with Far Hand which:

Target: One object that weighs 20 pounds or less and isn’t carried by another creature

Setting aside far hand (either impacting on the weapon increases weight or it counts as that creature carrying the weapon), the falling downwards onto weapons should either be an appropriate trap for the level (complete with the trap making an attack roll), presuming braced weapons, or should just be treated as a legitimate readied action. (Note that falling creatures don't provoke opportunity attacks, but can be the targets of readied actions assuming sufficient planning and communications.)

Answer 3

Do what's cinematic

While almost none of the specific example you gave actually works like that (which has been covered enough in Brian's answer and in comments on your original question), when you leave rulespace and enter improvisationland, the important thing is to have fun.

A lot of DMs use the improvised weapon rules for things like this. This is perhaps the closest thing to the rules, but I've always found it to be highly disappointing, as improvised weapons impose a severe attack penalty, don't necessarily use the right attack stat for your characters, and do frankly terrible damage compared to anything else your PCs could have done with their actions.

A good guideline is to make cinematic options -- a ballista on the airship you're riding on, knocking a pile of logs down a hill, blasting the ceiling of a cave to drop stalactites, knocking over a statue, or setting up a spike trap as you outlined -- either a skill check, an attack based on whatever stat someone can reasonably explain, or in many cases a d20 + a flat modifier. And damage should be somewhere between at-will and encounter-power tier, depending on the rarity of the situation.

Just to explicate where i'd use what, and reusing my earlier examples:

• firing a ship's cannon might be Level+5 vs fort and deal appropriate damage for a NPC ranged basic attack of that level, and might be available as a standard action as many times as any party member wants to do so. This option might allow strictly-melee characters to contribute meaningfully in an aerial or nautical battle with no melee combatants.
• knocking logs down a hill, depending on the situation could be either another flat bonus attack (if the logs were put there/prepared for this purpose, it would just be flipping a release and the logs would be essentially rolling the attack themselves) or a STR check/athletics check / other attack against the logs' support which subsequently leads to the aforementioned flat attack made by the logs. This could do more damage (i'd still use NPC damage tables if only for simplicity), as it could only be done once.
• for a spike trap such as the one you outlined, i'd have placing it be a skill check (anything you can reasonably explain) to set the DC of the acrobatics check required by the falling enemy to "miss" the spikes. If they failed and hit the spikes, the spikes would do 1x[W](whatever improvised weapon the spikes were made out of)per d10 of falling damage involved.

In situations where an enemy is indeed helpless, and thus eligible for telekinetic lift, it's hardly an issue to assume an auto-hit and instant fatality, if that's cinematic. This can't particularly be abused/reused to the point of imbalance, because helpless is a terribly rare condition to impose, and almost certainly leads to a gruesome death-by-coup-de-grace anyway.