Twotricks wrote:1. I would have 16 level of Wizard/Trickster levels, and would take Practiced Spellcaster feat.
Would I be able to cast lvl9 spells ? You need 17 levels of wizard to cast first lvl9 spell ?
Would my spellcaster lvl be 20 ?
You need 17 levels of 'Wizard Spell Casting Progression' to get your 9th level spell slots. You are stuck at 'Wizard Spell Casting Progression' of 16, so if you can squeeze out another level of Wizard or so, you will get your 9th level spells. Your caster level will be 20 though with Practised Spell Caster feat, it just adds 'Caster Level Progression'.
Twotricks wrote:2. If i have natural Int 18 , would I be able to cast lvl 9 spell if Int is boosted with equipment ?
Yes, as long as you have at least +1 intelligence from an item you will have access to 9th level spells.
Twotricks wrote:3. Reserve Spell feat : Invisible needle. I see Arcane trickster Wizards are taking it to sneak attack. Why is it better than attacking with ranged weapon or melee ? How many attacks in round can you make with Needle ? Does it expends spell slot when used ?
Basically, the reserve feats use trigger spells. If you have a trigger spell memorized, and do not cast the trigger spell itself, you can use the reserve feat as many times as possible. Just drag it to your hotbar for easy access.
Now, if you have a 9th level spell called 'Bigby's Crushing Hand' memorized, then your Invisible Needle will do 9d4 damage per cast. That is 22.5~ on avarage. (You can get sneak attack dice on top of it when you meet the ranged sneak attack/flanking conditions.)
If you do not have access to 9th level spells, you could use an 8th level spell called 'Bigby's Clenched Fist' to get 8d4 damage out of the Invisible Needle reserve feat. That would be 20~ damage on avarage.
Invisible Needle does magic damage, so it is rarely resisted. But you do have other options to consider as well. Such as
Acidic Splatter that deals 7d6 acid damage, 24,5~ on avarage, with the 7th level spell Greater Shadow Conjuration. And also,
Clap of Thunder that deals 8d6 sonic damage, 28~ damage on avarage, with the 8th level spell Greater Shout.
You get one reserve feat cast per round, so if you have the Two-weapon Fighting feats or Manyshot, you will likely do less Sneak Attack damage per round. The more hits you do per round, the more 'sneak attack' attacks you get. However, unlike with regular attack rolls, once you get past BAB of 15~, your Touch Attacks basically land whenever you roll above 1. (Or are not deflected by some form of concealment.)
Also, if you are an arcanist, it is always more fun to fling spells.
Twotricks wrote:4. Reserve Spell feat: Umbral Shroud. How good is it ?
It has a will save, it lasts for one round, it targets one target, and only grants you concealment of 40% with 'Mass Blindness and Deafness Memorized'. In otherwords, you are better off with just casting something like Concealment or Improved Invisibility on yourself to get 50% concealment against all enemies. I would pick any other reserve feat.
Twotricks wrote:5. What Epic spell would be most fitting for Arcane Trickster ?
To get Epic Gate, or other epic spells, you need to be able to cast 9th level spells. If you had higher Intelligence for spell DCs,
Mass Fowl could be right in your alley.
Epic Greater Ruin deals 175~ points of damage on avarage, which would be 87.5~ if the target makes its save. Not really worth it in my opinion. Thus mechanically speaking, the best epic spell to pick is Vampiric Feast, because it just drops HP to 50%. But if such evil spell does not fit your character, I guess Epic Gate is your best bet, if only to get a beefy tank for a while.
