Are Arcane Tricksters still limited to Enchantment/Illusion spell schools when multiclassing with a Wizard at higher levels?

Question

Please help me with Arcane Trickster Wizard multiclass spell options?

I have a Rogue-Arcane Trickster Lvl 10, Wizard-Bladesinger Lvl 6. I understand they use the other spell slot chart in the multiclassing section of the PHB. Now I know Arcane Trickster can only select Enchantment and Illusion spells. I also know you can add all spell schools in a Wizard's Spell book.

Are Arcane Arcane Tricksters still limited to Enchantment/Illusion spell schools when multiclassing with a Wizard as they gain more levels in Arcane Trickster?

Answer 1

Yes, the limitation still applies.

The Arcane Trickster's "Spell Known of 1st-Level and Higher" feature says:

The Spells Known column of the Arcane Trickster Spellcasting table shows when you learn more wizard spells of 1st level or higher. Each of these spells must be an enchantment or illusion spell of your choice, and must be of a level for which you have spell slots. For instance, when you reach 7th level in this class, you can learn one new spell of 1st or 2nd level.

The spells you learn at 8th, 14th, and 20th level can come from any school of magic.

Whenever you gain a level in this class, you can replace one of the wizard spells you know with another spell of your choice from the wizard spell list. The new spell must be of a level for which you have spell slots, and it must be an enchantment or illusion spell, unless you’re replacing the spell you gained at 3rd, 8th, 14th, or 20th level from any school of magic.

Being a Wizard does not change this in any way. Arcane Trickster levels only get you what the feature says they get you.

You only have one pool of spell slots.

Spell slots are spell slots. Multiclassing or not. See this question: Multiclass Spellcaster: Do the involved classes share the same pool of spell slots?

In particular, Please Stop Being Evil writes:

You only have one pool of slots

You cast whatever spells you can cast, in whatever manner you cast them. They use slots, which are a generic resource independent of your specific spellcasting class. There aren't 'Wizard' or 'Cleric' slots, for example - just 'spell slots'. So your PC might cast only Eldritch Knight spells with all their slots or only Wizard spells with all their slots or some combination of both.

Answer 2

There are a couple of parts here. The short answer is that you're still limited to illusion/enchantment spells when taking Rogue levels, but can copy any spell you can find (within level constraints) to your wizard spellbook.

Arcane Trickster spells
When you take a level in Rogue and get new spells, you can only choose spells from the Enchantment or Illusion schools (with exceptions at certain levels - see Thomas Markov's answer or PHB p.98 for the full text). These spells are not recorded in a spellbook. Per the multiclassing rules (PHB p.164), you determine the spells you know and prepare for each class individually. As a level 10 Arcane Trickster you'll know 7 spells of 1st or 2nd level.

Wizard spells
When you take a level in Wizard, you can learn spells from any school of magic. Additionally, you can record spells from any school of magic in your spellbook, provided that they're of a level that you could cast as a wizard. As a level 6 wizard, these spells can be from 1st to 3rd level.

Multiclassing spell slots
As a wizard 6 / AT 10, you are effectively a 9th level spell caster. This gives you access to a pool of spell slots up to 5th level. Provided a large enough slot is available, these can be used to cast any spells you know, regardless of the school or which class you learned it from.