Grey Kers ability says that he my change his declared action at any time during his turn. So if at the start of his turn can he declare a ready action and put guard on, then change this action to an advance, then move and attack while still keeping his guard order on? Or does the guard that he put on go away once he changes from a ready order to any other type of hero movement.

mc-hemmer said:

His cummulative 'activities' throughout his action must still at all times be legal within the bounds of his 'current' declared action. Nowhere in his special ability does it say he can 'take back', 'undo' or 'have fall off' activities that he has already done in order to make a desired Action change legal.
Since only a Ready action may place an order, once Grey Kerr Places an order he can't change his action to a non-Ready action because that would make his order placement illegal.

For example, he can't declare an Advance , move using his 'advance' MP, attack, find that he wants to attack again so declare that his order should be 'battle', and retroactively spend fatigue to pay for the MP he has already spent.
What he can do is declare an advance , (gaining a fatigue from Relentless skill if he has it), spend fatigue to move , attack , decide he wants to attack again and change his order to a Battle and attack again (keeping the fatigue from relentless, because Advance was still the order he Declared at order declaration time (he changes his declared action, not re-declares a new action)). He could not then activate Unmoveable (for the same reason) .
Or he could change to a Ready and place a Guard/other order marker .

Another thing to keep in mind (as clarified in the FAQ) is that only the first action Grey Ker declares counts as his "declared action." Changing it later is just changing, not re-declaring. This is important in cases where Grey Ker has multiple skills that key off declaring specific actions. ie: Grey Ker declares a Battle initially to gain a benefit from the Knight skill (I think that's the one), and then immediately changes his action to Advance. If he also has a skill that keys off declaring an Advance action he does NOT get that benefit. Even if he proceeds to take a normal Advance action for his turn, the first thing he declared was Battle.

Of course, the wording on skills like Knight completely fails to accommodate this situation. Grey Ker can declare a Battle, activate Knight, and then decide to actually perform, say, a Run. Knight says you "may make 3 attacks instead of 2 this turn." You now have to decide what effect that text has if the number of attacks you would have made during that turn isn't 2 (false presumption).

My recommendation would be to treat it as +1 attack, but an argument could be made either for setting your attacks to 3 (so Grey Ker can activate this skill to run and make 3 attacks) or for ignoring the text if the presumption is false (meaning that Grey Ker gains no benefit at all if he switches his action, unless he can somehow still make 2 attacks without using the skill).

The Descent writers have a strong tendency to write modifiers in the from of "change from X to Y" instead of relative changes like "+1", which quickly becomes a serious problem when you have multiple modifiers that take effect at the same time.

While I don't agree with it from a balance perspective, I'd have to argue that the accepted interpretation of Battle + Charge and Run + Quick Shot on Leiutenants would also mean Grey Ker could get 3 attacks and a Run in that case.

I believe you're thinking of Run + the "Rage" overlord card. Quick Shot is an ability possessed by, e.g., Manticores.

Rajamic said:

Knight also gives 1/2 movement, so it would have to be 3 attacks, 1/2 movement + double movement.

However I don't think this would be legal. Whatever else happens, by the end of Grey Kerr's actions, his accummulated activities have to be legal. If he changes from a Battle (3 attacks + 1/2 move) to a Run, at the end of the Action he must still meet the definition of a Run action, not a Battle Action. Since he doesn't get 2 attacks with a Run action, he can't use the Battle declaration to change 2 attacks to 3 attacks.
The problem with Knight is that it is a '3 attacks instead of 2'. So for it to still be legally 'kept' by the end of the turn Grey Kerr needs to still be getting 2 attacks in order to replace them with three attacks. Since the only way to do that is Battle (Rapid Fire and Quick Casting are immediate additional attacks so probably don't qualify - though I'm not really sure of this, maybe they would), he can't really change to a different order that only gives him 1 (or no) attack and keep the three from Knight.

It is a complicated situation not helped by messy wording.

For example, I think that an Able Warrior Advance declaration would see Grey Kerr able to spend the fatigue to make two attacks instead of 1. So as long as he ended up with a Ready (including an attack), Advance or Battle order he would be able to claim 2 attacks in place of one (with battle then having another attack of course).