Classic Monsters Revisited – The Tween (Fiend Folio)

While stocking the Hurricane Dungeon, one of the monster results came up as a tween from the AD&D Fiend Folio. That book is mostly a collection of monsters from the UK gaming magazine, White Dwarf, which covered a variety of RPGs in the early days before it became the house mag for Warhammer. Many of these creatures first appeared as submissions to the magazine's Fiend Factory column, by authors of varying levels of expertise and creativity.

Some are well-crafted and interesting, but most are simply variations on other monsters, with few distinguishing characteristics (other than appearance), or are just completely unnecessary. A handful of monsters were contributed by Gary Gygax, pulled from his previously-written adventures and added to what was essentially the second "monster manual" before the third monster manual became the official Monster Manual 2. Certain Fiend Folio monsters are passable-to-great; the rest are hit-or-miss (with lots of complete whiffs).

Having never used a tween before, I was eager to give it a fresh look. The tween's most interesting characteristic is a rudimentary form of 5e's Advantage/Disadvantage mechanic. (Perhaps even its "inspiration"?) The tween is essentially an ethereal "ghost" that attaches itself to a host, forming a shadowy doppelganger that provides a tremendous benefit to its host, but at a high cost to everyone else. The creature's presence is summed up with this wildly generous understatement: 

A character with a tween partner is therefore something of a mixed blessing to any companions.

That's because, while the tween's "partner" (it's host organism) gains the ability to make two dice rolls whenever a roll is required and take the better result, every other creature within fifty feet of the tween must do the same and take the worse result. This includes the tween host's allies. It's a "luck eater," basically, transferring the misfortune of others to the benefit of its host (and it, presumably). This looks awesome on the surface, but it has some enormous flaws.

 For one, by adding this to your campaign, you're doubling nearly every roll made at the table, on both the players' and the DM's side. The description of this ability reads:

(A)ny character or creature with a tween 'partner' has two die rolls instead of one, whenever a die roll is called for, and may select the more advantageous of these rolls. (This applies to 'to hit' rolls, saving throws and the like.)

The phrase, "...whenever a die roll is called for" is a bit ambiguous as to the type. (Is it all die rolls?) We can assume, based on the two examples provided, that the design intends for this to apply only to rolls made with a d20 (as is the case with Advantage in 5e), and not to rolls for things like hit points, weapon damage, etc.

But what about percentile rolls for success, such as for thief skills? The tween's description suggests that it is manipulating the environment around its host to make this "luck" happen (guiding the host's weapon, for example), so shouldn't it also apply to finding a trap or picking a lock? 

In any case, the result is a lot of extra rolling for the host and his fellow party members. And that's not even taking into account that the DM will have to roll twice for every single NPC and monster within 50' and run all those numbers as well. The game will inevitably slow to a dice-rolling, number-crunching crawl.

A second flaw with this design is that the tween's presence would be an intolerable situation for most players (I would think). I mean, if I were a player in this group, my character would have to deal with the situation in the short term until we left the dungeon and got back to base, but that tween-inflicted character won't be making a return trip (not with my guy, at least). 

I can't imagine any party of players accepting "bad luck" on every roll (according to statistical breakdowns of 5e Disadvantage, this equates to –5 or so on average). There's just no way. That's an enormous penalty in AD&D and a recipe for interpersonal conflict between characters (and perhaps even players). It will get someone killed eventually. I can see a character being forced out of a group over this situation, which sucks. It's one thing if the characters create that conflict themselves; it's quite another when a random roll forces it on them.

Worse still, the tween can't be countered by normal spell means, like Remove Curse. The description says that once a tween selects its host, it "...will remain permanently with him until he or the tween dies." That's pretty definitive, so it doesn't sound like the party can convince the creature to bugger off. The only way to be rid of the tween's luck effect is to enter the Ethereal Plane and kill it. But it's a Neutral creature ostensibly trying to help its host, which may pose a moral dilemma for Good characters (this is kind of cool). A lenient reading of one line gives DMs a bit of an out if they want to grasp it: 

The tween has the ability to see a few seconds into the future and is able to increase its host's luck.

Those two clauses suggest that perhaps this ability can be turned on and off by the tween, instead of being always-on. That would change the calculus dramatically, giving the player an incredible ability, but requiring them to use it situationally (mainly by separating himself from the party by 50' or more during combat... a tricky proposition). Still, a lone thief with such a tween would be a powerhouse. 

I don't believe that is the intent, though. I think this is just a dick-move monster, as designed. This is not an uncommon situation with the Fiend Folio.

I've kept the tween encounter in the Hurricane Dungeon to stay true to the dice rolls, and I'm curious to see what happens if one of my players ever "acquires" it. In the level 2 writeup, I adjusted the tween's effect to be a straight –4 / –20% penalty to others, so as to reduce the number of rolls the DM has to make. The host rolls twice for their bonus, and player allies can opt to either take the straight penalty or make two rolls at disadvantage instead.

For my home game, I may even alter the tween's effect even further to make it on/off (at will, triggered at the beginning of the round), and say that every time a player used the advantage ability, a single random creature — friend or foe — within 50' would suffer the disadvantage roll (instead of every other creature). 

That way, it's a bit more balanced and usable, and the number of extra rolls is kept to a minimum. I like magic items with caveats that make them somewhat dangerous to use, and this is like that. Fellow players may be able to more easily swallow the choice to accept a personal risk of penalty in order to give a comrade a big extra bonus in a critical moment (and potentially inflict the penalty on an enemy). It then becomes a tactical decision, rather than the "mixed blessing" of an arbitrary, likely-lethal, party-busting curse.