Surrounded by enemy crossbowmen being deadly - sounds like Warhammer Fantasy Roleplay to me. No parries, no dodge rolls, just a ranged percentile roll and serious damage. (Unless all PCs are decked with heavy armor)
Or maybe 1-3rd level D&D heroes, I guess. But beyond that, it's impossible without some special house rules.
Maybe something like this:
From time to time, a situation needs to be resolved in a way not following the normal rules.
Scenarios might be capturing PCs, hostage situations or duels. (typically anything that bypasses hit points)
In these scenarios, the DM pulls says "Dramatic Scene: <enter descriptive title here>".
Rules change: it boils down to a few checks and rolls by NPCs and PCs.
Basic framework:
- Roll Initiative:
- Everyone declares his intention for this round, from lowest initiative count to highest. (obviously, the higher ones can react to the intentions of the lower ones. Players and NPCs may roll bluff, hide, move silently, or sleight of hand to conceal actions, and opposing characters sense motive, listen or spot to reveal the true intention. (might also add rule for intimidation)
- Everyone resolves his action, from highest initiative count to lowest. Special: The DM may choose one roll (attack, save, skill check) to gain a bonus equal to the difference between the "normal" encounter level and the party level - if the encounter level is below the party level. If the encounter level is above party level, the party instead gets the difference as a bonus to one of their rolls.
Action resolution should now ignore most of the usual rules (hit points specifically)
- Reroll initiative for the next round. If a combat was started in the last round, the DM can decide to just continue regularly.
Example - 8 Crossbowman threatening the PCs:
Roll initiative as usual. Let's assume the PCs have different initiatives, some before, some after the crossbowmen. The lowest PC now has to decide - do I want to attack/flee? Depending on his decisions, the other PCs can attempt to form their actions - do they aid? do they try to avoid the worst? Should someone try to rely on diplomacy to stall the situation. The NPCs could choose to attack the PCs, or to demoralize them further...
Actions are resolved. Any attack (even with a spell or device) is resolved as a coup-de-grace (regardless of range), except that anyone failing his save is just reduced to -1 hit points and dying (if worse then the effect of the damage), as well as dazed for one round (in case someone heals him). Sneak Attack only applies if a target is flanked or flat-footed, though.
Example - Hostage Situation:
Basically as above, with the special notion that the goal of the PCs will probably be to kill the hostage taker, while the hostage taker is only interesting in taking the life of the hostage. Therefore, attacks on anyone not a hostage and not a hostage-taker can be resolved normal, but the attack on the hostage is fully deadly (as a normal coup-de-grace).
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For every dramatic encounter, characters get a "drama point", which means that they automatically get XP as if they just had beaten an encounter of their party level (in addition to the normal encounter). In addition it can be used to slightly alter the outcome of another dramatic scene (like determining that a hostage wasn't killed, merely severely injured and needs immediate medical attention, that a captured PC manages to hide an important item or ally to help him escape later, or whatever you want.)
You might also allow PCs to resist dramatic scenes in the first place, by rolling a level (maybe charisma-based?) check against the normal level of the encounter and spending a drama point. (point is only spend if check succeeds). PCs might also initiate a dramatic scene (taking their own hostage or just to increase the stakes of an encounter)
