Iām a little weary about Mordenkainenās Tome of Foes considering what Iāve seen of epic level monsters design in 5e. They just donāt seem to work well with bounded accuracy (rather than the super-escalation of 4e and 3e), and it seems like homebrewers just want to make their Broly; the invincible monster with 30 Strength and Constitution, AC 28, 600 HP, Immunity to elemental damage, resistance to everything else, Spell Save DC 28, +11 to all saves, magic resistence, and 5 legendary resistences, and 3 counterspells a day. They also get three attacks with +18 to hit, 50 damage a swipe, and an area of effect that is something like 50 damage a round. And a Draconic Presence variant to punish melee fighters and barbarians that canāt pass a DC26 wisdom save at disadvantage.
Iāve seen these fights, and they are boring as fuck. The entire party becomes a constantly retreating support system for a hasted, flying ranged fighter or rogue to plink away at the monster from longbow range since the design wonāt let melee fighters do their one thing (with +18 to hit AC essentially becomes irrelevant and the scalebreaking attack damage output and WOW murder auras makes it a death sentence without a healer assigned to everyone and a Paladin with Aura of Vitality up and somehow concentrated on). And the absurd saves, legendary resistances, counterspells, spell reflects, damage resistances, and Rakshasa-style by level spell immunities make any type of magic-user incapable of directly affecting their precious Broly.
Further compounding the boredom, most epic level 5e monsters designs (including Tiamat) have 50-80ā fly speeds and/or teleport effects, which pretty much negate any attempt at clever maneuvering or terrain-usage (or generation for certain magic users). Thus, the āgun planeā of the flying, hasted, advantage-buffed ranged attacker with a magic bow being the only thing that works.
If you want some good ideas for how to make an interesting high level monster, turn to 4eās high level baddies. They had fun effects that felt epic. Like dragons that could spend actions to intensify their next breath weapon, or giants that outright altered their surrounding terrain. I like the idea of that round of anticipation that proceeds the devastating effect. That feels epic, forcing the players to scramble for cover and come to terms with the new situation. Not a loop of claw, claw, bite, tail, save AOE, pass. Legendary action attack, legendary action ranged attack, legendary action spell.
