Does a Warlock receive the benefit of their familiar's Magic Resistance trait?

Question

The Warlock has access to special forms for their find familiar spell through the Pact of the Chain feature. I'm wondering if these special forms, the Quasit, Imp, and Pseudodragon in particular, allow the player character to share the familiar's Magic Resistance feature. In the Monster Manual each of these creatures has a sidebar that states that the familiar shares its Magic Resistance feature with the companion they are bonded to, but the PHB doesn't mention this in any of the creatures' stat blocks.

For example, in the Variant: Pseudodragon Familiar sidebar on page 254 of the MM it says:

"While the pseudodragon is within 10 feet of its companion, the companion shares the pseudodragon's Magic Resistance trait."

This feature seems clear in the MM but I'm led to believe that it wasn't intended for Player Characters since mention of it is absent from the stat blocks in Appendix D of the PHB (pages 307-309).

Would a 3rd level warlock who chose one of these familiar forms through the Pact of the Chain feature benefit from advantage from saving throws from spells and other magical effects due to these special forms, or was this feature only meant for powerful NPCs and enemy spellcasters who had made this link with these familiars themselves?

Answer 1

No, a Warlock with the Pact of the Chain feature does not receive Magic Resistance if they choose a Quasit, Imp, or Pseudodragon. In the first place, a variant rule is only in play if the DM chooses. However, even if the DM decides that pseudodragon familiars (for example) are a thing, it still doesn't benefit the Warlock.

Some pseudodragons are willing to serve spellcasters as a familiar. Such pseudodragons have the following trait.

So "some pseudodragons" will be familiars who share Magic Resistance with their masters. The Warlock, however, gets their familiar from the find familiar spell, which says:

You gain the service of a familiar, a spirit that takes an animal form that you choose: [...]

The Pact of the Chain says that:

When you cast the spell, you can choose one of the normal forms for your familiar or one of the following special forms: imp, pseudodragon, quasit, or sprite.

In other words, the Warlock's familiar isn't any sort of pseudodragon, let alone one with the variant. It's a spirit that takes the form of a pseudodragon (and can take a different form anytime the Warlock chooses). The spell does say that:

[...] the familiar gains the statistics of the chosen form [...]

However, the statistics of a creature are defined on pages 6-11 of the Monster Manual. The short definition is that, if you look at a creature's entry, it's everything in the yellow box. This doesn't include variant traits like the Familiar trait - those are in green boxes off to the side.

All of that aside, a generous DM could, of course, allow a Pact of the Chain familiar to provide its master with Magic Resistance. It must be pointed out, though, that this is making the Pact of the Chain vastly more powerful than it normally is, so DMs thinking about it should consider carefully.

An even more generous DM could allow any player to gain the service of a creature with the familiar variant. This, too, should be considered carefully - it's effectively giving the player a more powerful version of the Pact of the Chain feature for free.

Answer 2

These are separate sources which are meant to be read independently of each other. One familiar is a spirit in a corporeal form and the other is an actual named Fiend, Fey, Dragon, Devil.

Find Familiar spell states:

"... the familiar has the statistics of the chosen form ..." (PHB pg. 240)

Statistics refers to:

A monster's statistics, sometimes referred to as its stat block, provide the essential information that you need to run the monster. (MM pgs. 6 - 11)

Variant: Familiar (DM Approved)

VARIANT: QUASIT FAMILIAR

Mortal spellcasters interested in extraplanar familiars find quasits easy to summon and eager to serve. The quasit plays the part of the obsequious servant. It serves its master well, but it goads the mortal to greater and greater acts of chaos and evil. Such quasits have the following trait (not retained by FF spell).

Familiar

The quasit can serve another creature as a familiar, forming a telepathic bond with its willing master. While the two are bonded, the master can sense what the quasit senses as long as they are within 1 mile of each other. While the quasit is within 10 feet of its master, the master shares the quasit's Magic Resistance trait(*). At any time and for any reason, the quasit can end its service as a familiar, ending the telepathic bond.

Is about acquiring the actual creature by other mean referred to by summon. You would not gain the Find Familiar features, like use an action to look through the familiars senses. And vice versa, Find Familiar does not gain Magic Resistance Trait

Being this is a Variant ruling for the DM it only applies if the DM allows it. Otherwise, you are stuck with the Find Familiar version.

Lastly, if I'm not mistaken, the lastest version/publishing trumps previous ones with duplicate rulings, ergo MM trumps PHB for stats. In addition, the DM would / should refer to the MM when he tells / gives you the statistics for said familiar creature form. You have the option of choosing the form, not the stats.