Fellow GMs and those who wandered in here by mistake, I approach the bench to converse with others of a matter most troubling to me as a master of ceremonies, story and authority.

I have recently encountered some resistance in a game I am in motion with. If they are reading this they will know who they are and advise we don't have this out here. I find many of the rules very illogical or ill fitting at times and lately have begun to override them. When I do this many a time it is for the nature of what smooths the plot along and avoids it being bogged down in terminology or having to spend ages searching rulebooks but I have also used them to allow me as a GM to pull off some (what I would consider) fancy moves and showing off.

Case in point, a Tau opponent was caught in grapple with a brother marine on it's back trying to restrain it. I opted for what I considered was a tactically sound move which is to try and smash backwards and crush the marine between itself and the floor. I mean what else can you do with q guy on your back? One of my number disagreed with this move arguing that it was not one of the approved three for when the Tau is the grappled target and therefore couldn't be actioned. After some debate I managed to seize the decision but at cost to what I fear was my credibility and it was begrudgingly accepted.

My question then is not so much in relation to this example but a general point. Should a GM be free to disregard or alter any number of rules required to suit the plot or story if it makes the game flow more effectively and as long as they will allow players and future NPC to be subject or benefit to any house rule he changes or should the book be absolute, providing clear definitions for players?

This decision most troubles me since they are a good group but I am concerned my desires to create an entertaining and thematic setting are frustrating those who value accuracy and that to follow them all may hamper the way I work.

Yes, but tell them first, and give them the same options the NPCs have. It works well for me, because it's a convention at my table that, if you want to do something creative and cool, you just say it and I'll tell you what to roll. I play it fast and loose with the rules, because the rules don't cover everything, but I make sure my players know this.

If you just spring new things on people, they'll tend to react poorly, especially if it's to their detriment.

In the example in question, I would hazard to say that the Tau may try to do so, but in a space marine's grapple, would have little chance, because Tau are feeble weaklings and a marine has a much greater mass. It simply wouldn't work unless the Tau is in a crisis suit. Now, if the marine was trying to grapple an Ork? Different story, and generally a bad idea.

I know you said to disregard the example per se, but I will use it to illustrate players have expectations of how the setting acts. These will not always mesh with your own, but it pays off to cater to stereotypes, and just, say, let them destroy a Tau in melee. Have them be smart and creative at range instead, where the players will expect competence, and perhaps appreciate some creativity since it caters to what they expect from the Tau. As a notable Lord Vetinari once said: "People don't want news, they want olds." So you got to know their expectations and tie them into your campaign and NPC behaviour. Have the surprises be logical, and allow for quick thinking to anticipate them. For example, if they're dead convinced that a certain spot is an ambush, and it actually makes tactical sense for the enemy to set one up there, have there at least be a few sentries or a sniper "covering" the approach, if you had absolutely no one there prior. If it doesn't make sense for there to be whatever the players imagine there is, at all, of course, don't do this .

Good advice by Death by Grotz.

Basically communication is key. GMs generally put in the lions share of the work in preparing the game for the players entertainment. Often they are the ones spending the money on source books as well. This does give them a certain level of entitlement to arbitrate, and make up new rules.

However a player doesn't have to play! So a GM needs to keep players on board. That generally means being consistent and fair with rules changes and crucially telling the PCs when rules are going to change.

In the example you gave it might have felt quite arbitrary for the Tau to try that move. Though strictly I don't think it is against the rules as it would be covered by movement I think. In any case how you handled it makes a difference. A Tau with a marine on his back attempting to force the marine onto his back is unlikely if not impossible. Basically the marine should be getting major bonuses for size and weight. Basically it would be a hellish task for the Tau less than this and I could see why your players are aggrieved .

Context is probably more helpful so it doesn't seem like me being mean.

Marine was out of armour and the Tau was in an XV22 suit variant. Roughly the same in terms of height and stature. It was therefore safe to assume that the both are pretty evenly matched in their prospective states.

Definitely. A crisis suit is essentially a Tau dreadnaught. Perhaps that comparison would explain the situation better to the player? It does help to use the frames of references their characters might have to illustrate it, as well as giving them the chance to reconsider. For example, tell him that the crisis suit seems to possess the inhuman strength of a machine, much like a dreadnaught, and that sans armour, he has to exert all his strength to keep it down. Illustrate his position is precarious, give him the chance to react and if he just keeps on going, you've done enough setup that he knows something is coming.

Yeah if he was in a suit I don't see anything wrong with it at all. If it was just a normal tau vs a SM I'd rule I'd either just rule in player's favor and say it can't happen, or give the player the appropriate grapple bonus, which I think is +10 for differing sizes.

Ultimately when it comes down to it. You just have to sorta talk to your players about what you expect, not just of the setting but in rulings. My players generally know how I'm likely to rule. I will favor the player anytime I'm not sure which interpretation of a rule is correct, or just make a roll up if we're not conflicting and just confused. Sometimes when a player is moaning about my ruling, I might throw them a bone and give them a bonus, but that's it. That's my dynamic though, and my understanding from a fairly long standing game. Just talk with them is the best option.

Thank you for the insight fellows. I do usually try to favour the player somewhat while at the same time make decisions to keep the story going although this one was me leaning heavily on the side of the major plot antagonist because it was an unexpected combat and I wanted to pull them out of the fight early.

What I always try to do is that whenever I make a house ruling to change something which is particularly dubious, I will force myself to abide by the same rules. For example I'm using hybrid rules with elements of Deathwatch but also the Black Crusade/Only War manner of handling things like Psychic Powers, attack rolls and characteristics. I find that the newer systems create much more balance, for example changing Unnatural characteristics to additives rather than multipliers. Getting bonuses to hit based on single careful shot with penalties for spray and pray etc. I've forced my NPCs to do the same as well usually.

Yeah I totally get that. It's easy as a GM to overreact when surprised. I usually try to keep it from being too cheesy and something reasonable, I ask my guys to give me a headsup if they're planning on (a specific) duplicitous murder so I'm not flatfooted, and of course I'm likely to give them the "Are you sure you want to do that," on occasion. And give them a bit more information that maybe their character would be privy too that I maybe hadn't yet made clear(the Governor will attack if you say that/this guy is fishing for a bribe/etc). Never a veto, just making clearing up what I think are likely immediate consequences that they may not have considered.

This normally works out. I'm able to come up with a slightly more thoughtful outcome to their schemes, something better than "He runs away instantly/shoots you in the face with a plasma pistol". The line of how much if any of that works is up to your group.

What you did wasn't wasn't much of a stretch, but I'm not in your game and I wasn't in the room so I can't really comment. One thing I can suggest is fate points. Important characters get fatepoints so the PCs can mechanically weaken him if they succeed, and you're not worried about them killing the primary antagonist during the first 10 minutes of the adventure. Which floats some boats, mine too depending on context. And honestly taking a 5 minute break to figure out what to do is not really what any GM wants to do, but it's often a good idea.

In general, grappling I find is poorly done in just about every game system. Trying to be plausible just leads to an endless fractal of realism vs RaW. Better to stick to the rules unless you really want to spend time recrafting the whole section from scratch.

Slamming him could be an abstract of taking control of the grapple.