1. It allows for some things in Tasha's, like Custom Lineage (ASI bonuses where you want them). I'm assuming this allowance does not make Tasha's your +1 book, correct?
2. If I use a class from Tasha's, such as Eloquence Bard (which is also in MOoT) or Scribes Wizard, does THAT make Tasha's a +1 book?
3. Same question for Tasha's optional feats and spells.
It matters which AL campaign you are playing with the character.
If you are playing Season 10 - Rime of the Frost Maiden - hardcovers, modules or dungeoncraft content then the PHB+1 rule still applies except that the list of races allowed for Season 10 are explicitly listed in the Season 10 AL Player Guide.
Answering your questions IF you are playing a Season 10 character:
"1. It allows for some things in Tasha's, like Custom Lineage (ASI bonuses where you want them). I'm assuming this allowance does not make Tasha's your +1 book, correct?"
This is NOT Custom Lineage. Custom Lineage is not allowed in any AL campaign.
"Custom Lineage These rules aren’t used in Adventurers League play."
The rule that you are referring to is called "Customizing your origin" and it is allowed.
"2. If I use a class from Tasha's, such as Eloquence Bard (which is also in MOoT) or Scribes Wizard, does THAT make Tasha's a +1 book?"
Yes.
"3. Same question for Tasha's optional feats and spells."
Yes. Except for a feat chosen at character creation (like a variant human). Choosing spells from Tasha's will also make it your +1.
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However, there are also the Masters, Historical, Eberron and now Mist Hunters campaigns.
The PHB+1 rule no longer applies to Masters, Historical or Eberron. Characters for these campaigns can freely choose options from the sources listed as acceptable for these campaigns without consideration of which book the content comes from (Mist Hunters has special character creation rules that may differ). However, you need to check which sources are allowed in each campaign. For example, SCAG and other forgotten realms sources are not available when playing Eberron. However, all three campaigns include PHB, XGTE and TCOE.
Rules for character creation: PHB + 1 Published Book. Here are how Tasha's options apply:
https://media.wizards.com/2020/dnd/downloads/dnd_tcoe_alguidance.pdf
1. It allows for some things in Tasha's, like Custom Lineage (ASI bonuses where you want them). I'm assuming this allowance does not make Tasha's your +1 book, correct?
2. If I use a class from Tasha's, such as Eloquence Bard (which is also in MOoT) or Scribes Wizard, does THAT make Tasha's a +1 book?
3. Same question for Tasha's optional feats and spells.
Thanks for any help!
I think PHB+1 is on its way out. It isn't used in historic (non-seasonal) anymore.
(in red) But I can still play Eloquence Bard because it's also in Tasha's, correct?
Thank you for the help, BTW
Correct. After Tasha's only a few specific races are setting locked now (and dunamancy).
It matters which AL campaign you are playing with the character.
If you are playing Season 10 - Rime of the Frost Maiden - hardcovers, modules or dungeoncraft content then the PHB+1 rule still applies except that the list of races allowed for Season 10 are explicitly listed in the Season 10 AL Player Guide.
Answering your questions IF you are playing a Season 10 character:
"1. It allows for some things in Tasha's, like Custom Lineage (ASI bonuses where you want them). I'm assuming this allowance does not make Tasha's your +1 book, correct?"
This is NOT Custom Lineage. Custom Lineage is not allowed in any AL campaign.
"Custom Lineage
These rules aren’t used in Adventurers League play."
The rule that you are referring to is called "Customizing your origin" and it is allowed.
"2. If I use a class from Tasha's, such as Eloquence Bard (which is also in MOoT) or Scribes Wizard, does THAT make Tasha's a +1 book?"
Yes.
"3. Same question for Tasha's optional feats and spells."
Yes. Except for a feat chosen at character creation (like a variant human). Choosing spells from Tasha's will also make it your +1.
-------------
However, there are also the Masters, Historical, Eberron and now Mist Hunters campaigns.
The PHB+1 rule no longer applies to Masters, Historical or Eberron. Characters for these campaigns can freely choose options from the sources listed as acceptable for these campaigns without consideration of which book the content comes from (Mist Hunters has special character creation rules that may differ). However, you need to check which sources are allowed in each campaign. For example, SCAG and other forgotten realms sources are not available when playing Eberron. However, all three campaigns include PHB, XGTE and TCOE.
Documentation can be found here: https://dnd.wizards.com/ddal_players