How do Summon Monster spells work from lore perspective?

Context: I plan on GM’ing a long campaign in MtG universe. Most of my players will become planeswalkers at some point (full-progression casters rules-wise) and will travel throughout universe a lot.

This is when I realized that I completely lack knowledge on how the bread-and-butter part of MtG universe really works, which is summoning. In D&D this comes down to a simple series of spells: Summon Monster, and variants of it. And this is what I want to focus on here.

My problem with Summon Monster comes down to several key aspects of it that are not described in D&D rulebooks. All of those aspects have a source in a single question: whether what is summoned is actually a creature from another plane or just copy of it, magical dummy that does what it was told to and vanishes?

If it’s indeed a creature from another plane being summoned (which most opinions around the web seem to point at) this raises a series of storytelling problems, established lore plot-holes and power level concerns. I’ll try to list those issues here:

  1. How are creatures to be summoned chosen? Can every creature in universe that has an outsider type be summoned? Can players playing tieflings and aasimars be summoned too?
  2. Does a summoned creature have a say in whether it wants to be summoned in the first place? Can You just pull a creature out of it’s own plane at any moment in time? As funny as it sounds, majority of summoning situations would be either during eating, pooping, sleeping or having the fun-time. Not exactly pretty picture.
  3. It also raises another concern. Whatever the creature was doing at the time of summoning is left unattended. This means summoning have a potential of mass destruction, simply by pulling out guards off their posts, builders off their work, sailors off their ships, etc.
  4. Does a summoned creature have a say in whether it wants to follow orders? Can You keep sending let’s say celestial creatures against their own kin? If that’s the case conquering other planes would be as simple as summoning half of it’s inhabitants to fight the other half.
  5. Last but not least there’s a power level issue. From the perspective of simple combat situation Summon Monster seems like an average spell. Gives a temporary meatshield so caster can focus on casting instead of running from enemy. But when You look from the perspective of all I mentioned above, this is basically a planar travel combined with mind control, both of which are high-level endeavors. How can a low-level caster accomplish something like that?

So with all of the above in mind, I’m asking for a comprehensive, detailed description of how Summon Monster spells work in D&D or MtG or both (since after WotC married the too there are intersections) that addresses all or most of the issues I listed above.

I’m only interested in official content (for example official D&D rulebooks/setting books, official D&D novels, official MtG novels).

I’m also aware this is a very complex topic and I might not worded it perfectly so if someone wants to edit the question to be better, feel free to do so.

How much XP does a monster created by Animate Objects add to an encounter?

I am making a boss fight. The boss can cast animate objects, a spell that can animate statues.

The spell gives information for, eg., 1 Large Construct:

Large – HP: 50, AC: 10, Attack: +6 to hit, 2d10 + 2 damage, Str: 14, Dex: 10

How much XP should I award for this Large construct?

I’m estimating CR1 (200XP) each.

Do named actions in monster statblocks use the Attack action?

This question is inspired by the following and stems from wondering whether the Steel Defender’s "Force-Empowered Rend" action involves taking the Attack action:

  • Can a hasted steel defender benefit from its extra actions?

Take the Lich for example, It has an action titled "Paralyzing Touch"; does this involve the Attack action? Similarly, the Ogre has the "Greatclub" and "Javelin" actions; do these involve the Attack action? Does the Adult Black Dragon’s "Acid Breath" involve the Attack action? How does one know if something listed under "Actions" in a monster’s statblock involves taking the Attack action or not?

This matters for various features that key off of taking the Attack action while somebody is polymorphed, shapechanged, Wild Shaped, or by some other means has become one of these creatures while maintaining their class features such as Extra Attack or the Monk’s Flurry of Blows.

Beginning at 5th level, you can attack twice, instead of once, whenever you take the Attack action on your turn.

Immediately after you take the Attack action on your turn, you can spend 1 ki point to make two unarmed strikes as a bonus action.

The only thing I have managed to find that I think might be relevant is the following SAC ruling:

Q. Can you use a melee spell attack to make an opportunity attack? […]

A. […] A few monsters can make opportunity attacks with melee spell attacks. Here’s how: certain monsters—including the banshee, the lich, and the specter—have a melee spell attack that isn’t delivered by a spell. For example, the banshee’s Corrupting Touch action is a melee spell attack but no spell is cast to make it. The banshee can, therefore, make opportunity attacks with Corrupting Touch.

Note that this question is different from my previous question:

Does using an Owl's "Talons" action while Wild Shaped count as taking the Attack action?

The question failed to ask what I actually wanted to ask. It happened to be asking about an action that could effectively be accomplished through unarmed strikes and was not explicitly asking about things like the Lich’s Paralyzing Touch and a Dragon’s Breath. This question, in contrast, is asking about such features explicitly.

Can you train a hydra after using Charm Monster?

So my plucky halfling street performer bard is whisked away to a magical land and lands in a tropical beach. A six-headed hydra assails the party from the surf. In response, my halfling softens it up with a dirge of doom and successfully enchants it with Charm Monster. I’m level 10, so in theory it is now a nice, friendly hydra for ten days.

So, the question: Can I use Handle Animal or any other mechanic to domesticate the beast and get me a pet-six headed hydra?

Does Ranger Monster Hunter’s Slayer’s Counter works on saves to maintain concentration?

From the Sage Advice Compendium:

Does a Monster Slayer ranger’s Supernatural Defense feature apply if a creature damages the ranger, thus causing the ranger to make a Constitution saving throw to maintain concentration on a spell? Yes.

Since the Supernatural defense works for concentration, does the Slayer Counters works as well?

Stealthiest Monster in DnD

We are a level 20 party about to embark on a stealth mission. My wizard has bad stealth so I’m trying to find the most undetectable creature I can find to polymorph into. By undetectable I mean high stealth, invisibility and teleportation abilities, entering the ethereal plane, just anything that lets me avoid detection in whatever way?

Are the monsters in the MM actually following the monster creation rules?

The guidelines for making your own monsters are based around the Monster Statistics by Challenge Rating table on p274. Inspired by this question regarding Animated Armor (MM 19), which is CR1, let’s see where the Armor would be if we made it from scratch…

Defensive CR: The Armor has 33 HP, but step 9 (Damage Vulnerabilities, Resistances and Immunities, DMG 277) has us adjust effective HP based on resistance.

So we start with 33 HP, giving us CR 1/8, which tells us that we’re using the first line of Effective Hit Points Based on Resistances and Immunities, for an x2 multiplier for each Resistance or Immunity.

The Armor has two Immunities, so has 33x2x2 or 132 “effective” hit points. That puts us at CR 5. We then look at its AC of 18, which is 3 higher than the normal 15 for CR 5. That adjusts us up by one, to CR 6.

Offensive CR: It does 10 (2×5) points of damage, for a CR of 1. Its Attack Bonus is +4, which is 1 higher than the normal +3, but doesn’t adjust CR up.

Final CR is the average of the two, or (6+1)/2. That gives us 3.5, which we round against the players, for a final final CR 3.

How is Animated Armor a CR1 challenge? Its only notable disadvantage (from a combat perspective) is its Antimagic Susceptibility, but that has no effect on CR, per DMG 280. What’s knocking it down from CR 3 to CR 1? Or am I horribly misunderstanding how the creation rules work?

Is it possible to turn a monster into a humanoid without giving them average physical ability scores?

Savage Species lists some rituals through which a creature can–in one example given–transform from an ogre into an elf.

If nothing else, it’s an interesting and evocative idea: a 6th level ogre barbarian who tires of racial prejudices and transforms into an elf. His RHD disappear, and he becomes a 6th-level elf barbarian. His lower effective level means he can no longer travel with ECL ~12 parties, but he decides to do it anyway. Heck, maybe he did it partly because he was tired of that +2 LA that Savage Species likes to pretend isn’t a big deal.

Unfortunately, losing all those hit dice is far from the worst thing that happens to him. Doing any of the book’s major rituals means his physical ability scores become, at best, 11/13/9. Considering his ogre-born mental scores aren’t picking up much slack either, this is pretty much unacceptable for a barbarian in all but either very silly or very gritty games.

Is there any printed way around this, or to compensate for this beyond things like wishing for inherent bonuses and equipping magic items (which any high level barbarian is going to get anyway, so the transformed elf barbarian still finishes with noticeably poor scores)?

Was the Monster Lore Compendium ever updated after April 6th, 2008?

Was the Monster Lore Compendium ever updated after April 6th, 2008? If so, where can it be found?

I have read that it was going to be added to the d20pfsrd (yes, d20pfsrd, even though this is a 3.5e resource), though I don’t think that ever happened.

I know it was put into a spreadsheet here but I don’t believe that any updates were added.