ok lets get a few things cleared up. . .

one:
i summon mobius
is priority optional?
meaning as soon as i summon him can my opponent ask me if i call priority?
if i do call priority and i select 2 out of 3 s/t cards can he activate bottemless?

two:
and continuous trap cards
ive seen discussions about these kinda cards and i heard that under certian circumstances u cannot activate the effect of a continuous trap card right after activation. or when its in a response to an attack

three:
i have guardian kay'est on the feild face up.
and another monster with higher attack.
my opponent activates fissure.
kay'est is uneffected by spell cards yet she is the lowest atk.
so does the effect of fissure disapear? or does it distroy my other monster?

so if im speaking english here could i could some of these cleared up?
thanx

I'm not that particular with #1, but I can answer #2 and 3.

#2 - It depends on the trap card, take for example appropriate, you can only activate it when ur opponent draws a card outside his/her draw phase, but the effect sets in the second time ur opponent draws outside his/her draw phase.
- Another is call of the haunted, ... you know what i mean here.

#3 - Ya, the effect of fissure disappears, since the lowest atk monster u hav is kayest, but she can't be affected by ANY spells.

For question #1, whoever activates Mobius' effect gets to choose two spell/trap cards. Then the opponent gets to chain whatever.

1. Mobius is not an Ignition effect, it is a Trigger effect, therefore as soon as it is Tribute Summoned his effect will trigger, there is no priority issue with Mobius.

2. It means that if there is a continous trap activated in the middle of a chain, for instance:

Chain Link 1: Pot of Greed
Chain Link 2: Skull Lair (continous trap cannot activate effect still)
Chain Link 3: Return from the Different Dimension

this means that in order for you be able to activate Skull Lairs effect until the current chain ends.

3. The effect dissapears.

1. Mobius is not optional as it activates as soon as it is Tribute Summoned. The only option you have is how many targets you wish to destroy when it resolves.

And, yes, AFTER the targets are selected, the opponent can chain to Mobius' effect with Bottomless Trap Hole as the timing for it is STILL correct (Mobius being summoned). So Bottomless Trap Hole would destroy Mobius and remove it from play and then Mobius would destroy Bottomless Trap Hole and the other target, assuming there is one (Mobius does NOT have to remain face-up on the field for its effect to resolve).

2. see wraith's post

3. Being "unaffected by Magic Cards" (or Trap Cards) does NOT mean that things do not automatically redirect away from them nor "negate" them in any way.

In this case, Fissure will ATTEMPT to destroy Guardian Kay'est since she has the lowest ATK strength, but since she is unaffected by the effects of Magic Cards, it merely resolves without effect (so nothing is destroyed).

I would like to point out that Mobius is considered to be an OPTIONAL trigger effect as it says " . . . you CAN destroy up to . . . " on the card.

This makes a difference when you are forming chains and also if it misses its timing.

To say that it's not optional would be incorrect.

Well, the "not optional" part is mainly because, unless it misses the timing, when Tribute Summoned, you HAVE to decide how many targets to destroy. 0, 1 or 2. You cannot Tribute Summon it and decide for nothing to happen at all.

well, i'd like to argue with you on that hdi, since if it can miss its timing it must be an optional trigger effect, which means you have the option of not even letting it activate.

but i don't see a point in arguing over the difference between choosing not to ativate it, or choosing to activate it and select 0 targets.

since the only time it would matter is if divine wrath was to be chained to it. although i guess it would be a pretty important point in that case.