"All keywords" means "one instance of each keyword." It can be overcome by enough "gains X keyword" effects.

If a specific keyword or a specific category of keywords is named (i.e., "loses all Stealth" or "loses all non-immunity keywords"), then character could not have that keyword/type of keyword and the effect could not be overcome with "gains X keyword" effects.

Ktom, since we never really heard from you in response to http://www.fantasyflightgames.com/edge_foros_discusion.asp?efid=18&efcid=4&efidt=749349&efpag=1, it would seem that at last ruling from FFG "All keywords" is "All instances of all keywords" (although I'm still not sure if a second lost-oasis used after works).

Eh. If they are shifting the rulings, they are shifting the rulings. This was always one of those "both interpretations can be defended" situations.

If the ruling is "'all keywords' means 'all instances,'" then the second Lost Oasis will not work. Just like STR and icons, you always do the calculation from scratch each time. Since Pentoshi Manor has been ruled to mean "all instances," its factor in that calculation will be variable, not fixed at the time it is triggered. In fact, it is probably better to think of Pentoshi Manner the way you would the Bara-Iron Throne and Dominance. Technically, you still do the count, but the card effect defines the final result, no matter how the count actually turns out.