A 10th stage Drow warlock (as an example) has the next Drow Magic racial trait (PHB p. 24), along with its warlock spellcasting talents:
You understand the dancing lights cantrip. Whenever you attain third stage, you may solid the faerie hearth spell as soon as per day. Whenever you attain fifth stage, you may as well solid the darkness spell as soon as per day. Charisma is your spellcasting means for these spells.
Can the Drow warlock solid faerie hearth (which isn’t on the warlock spell checklist) utilizing a warlock spell slot?
Can it solid darkness (which is on the warlock spell checklist) utilizing a warlock spell slot?
The Sage Recommendation Compendium says this concerning the Magic Provoke feat:
In the event you’re a spellcaster, are you able to choose your individual class once you achieve the Magic Provoke feat? Sure, the feat doesn’t say you may’t. For instance, for those who’re a wizard and achieve the Magic Provoke feat, you may select wizard and thereby be taught two extra wizard cantrips and one other 1st-level wizard spell.
In case you have spell slots, can you employ them to solid the 1st-level spell you be taught with the Magic Provoke feat? Sure, however provided that the category you choose for the feat is one in every of your lessons. For instance, for those who choose sorcerer and you’re a sorcerer, the Spellcasting characteristic for that class tells you that you need to use your spell slots to solid the sorcerer spells , so you need to use your spell slots to solid the 1st-level sorcerer spell you be taught from Magic Provoke. Equally, in case you are a wizard and choose that class for the feat, you be taught a 1st-level wizard spell, which you might add to your spellbook and subsequently put together.
However this particularly requires you to select the feat for one in every of your lessons to have the ability to solid the spell learnt utilizing your class spell slots, and doesn’t appear straight relevant.
A Warlock can use warlock Pact Magic spell slots to solid spells learnt from ranges of one other spellcasting class, per the multiclass spellcasting guidelines (PHB p. 164):
In case you have each the Spellcasting class characteristic and the Pact Magic class characteristic from the warlock class, you need to use the spell slots you achieve from the Pact Magic characteristic to solid spells or have ready from lessons with the Spellcasting class characteristic, and you need to use the spell slots you achieve from the Spellcasting class characteristic to solid warlock spells .
Equally, if the warlock has learnt the invocation Masks of Many Faces (PHB p. 112)…
You may solid disguise self at will, with out expending a spell slot.
…Can the warlock solid disguise self utilizing a spell slot, e.g. to lower the possibility it may be dispelled?