Is this epic-level pet NPC something I shouldn't have in my back pocket?

[Grindy-high]

I keep this guy around to punish unruly players when I DM. Have I gone too far?

Mongo CR 28
XP ???
Nephilim Fighter 20
N Large outsider (native)
Init +5; Senses darkvision 60 ft.; Perception +41
DEFENSE
AC 22, touch 10, flat-footed 20 (+6 armor, +1 Dex, +6 natural, –1 size)
hp 346 (31d10+186)
Fort +27, Ref +10, Will +21; +7 vs. fear and sorrow effects
Defensive Abilities bravery +5, soul of sorrow; DR 10/magic; 5/-; Resist cold 10, fire 10; SR 19
OFFENSE
Speed 30 ft.
Melee +5 greatsword +47/+42/+37/+33 (4d6+21/17–20) or 2 slams +39 (1d8+9)
Ranged mwk spear +40/+35/+30/+25 (4d6+13/×3)
Space 10 ft.; Reach 10 ft.
Special Attacks crushing blow, mortal challenge, weapon mastery (greatsword), weapon training (heavy blades +4, spears +3, hammers +2, light blades +1)
STATISTICS
Str 29, Dex 13, Con 22, Int 16, Wis 18, Cha 17
Base Atk +31; CMB +41 (+45 bull rush, sunder); CMD 50 (52 vs. bull rush, sunder)
Feats Awesome Blow, Cleave, Cleaving Finish, EnduranceB, Great Cleave, Great FortitudeB, Greater Sunder, Greater Weapon Focus (greatsword), Greater Weapon Focus (spear), Greater Weapon Specialization (greatsword), Greater Weapon Specialization (spear), Improved Bull Rush, Improved Cleaving Finish, Improved Critical (greatsword), Improved Initiative, Improved Lightning Reflexes, Improved Natural Armor, Improved Natural Attack (slam), Improved Sunder, Power Attack, Quick Draw, Step Up, Toss Foe, Weapon Focus (greatsword), Weapon Focus (spear), Weapon Specialization (greatsword), Weapon Specialization (spear)
Skills Bluff +25, Climb +28, Diplomacy +40, Intimidate +40, Knowledge (geography, planes) +25, Perception +41, Sense Motive +41, Stealth +21, Survival +26, Swim +22
SQ: armor training, armor mastery 4
SPECIAL ABILITIES
Crushing Blow (Ex) When Mongo makes a successful critical hit with a melee attack, the target must make a DC 24 Fortitude save or take an additional 3d6 points of nonlethal damage and be staggered for 1 round. The save DC is Strength-based.
Mortal Challenge (Su) When Mongo spends a standard action to roar a battle challenge, all humanoids and monstrous humanoids within 100 feet of Mongo must make a DC 18 Will save to avoid becoming frightened for 5d6 rounds. On a successful save, the creatures only become shaken for that time. Creatures with more HD than Mongo become shaken if they fail their save, and suffer no effect if they succeed. A creature that succeeds at the save is immune to Mongo’s mortal challenge for 24 hours. This is a mind-affecting fear effect. The save DC is Charisma-based.
Soul of Sorrow (Ex) Mongo gains a +2 bonus on Will saves against fear effects and any effect that causes sorrow.

[DM_Kumo Gekkou]

What level are you throwing him against?

[hogarth]

Step 1: Cast Grease on his +5 greatsword.
Step 2: When he drops it, grab it and run like hell!
Step 3: Profit.

[EldonG]

CR 28?

Seriously?

More like a 20.

AC 22 is comparable to 8-9...his HP are in line with 19-20...damage only a little high. Yeah, his combat maneuvers are pretty sick...but he's so easily defeated...

[Peachbottom]

Unless I'm missing something, this creature does not seem like it is truly a CR 28.
With an AC of only 22 and minor DR, melee types will have no trouble hitting or damaging it. And with SR of 19 and a Reflex save of +10, caster types will have no trouble blasting it. A party of four that can deal average 100 damage each, which isn't that hard, can take this guy out in one round.
SR is usually 10 + CR so I'd increase that a little. I'd probably also give him more armor or natural armor to help him survive.
His damage and special abilities look good though.

[ub3r_n3rd]

Yeah, I agree he's pretty weak in the defense area. He's all about yelling at you and then combat maneuvers. A silence spell gets rid of his Mortal Challenge and anyone with range can pretty easily pick him off. I think a gunslinger targeting his touch AC of 10 (pretty much only a 1 misses) or an archer would pwn him hard given a full round action and the ability to bypass his DR. A pary of level 15's working in together would kill him in a round or two at most I think, he might be able to kill one of them if he got close enough.

[Grindy-high]

The party in question is level 12. There are two rogues, a titan mauler barbarian, a cleric of shelyn, and a sandman bard.

I want his very presence to intimidate them into following the right path, and hopefully hold up in battle if they try to pass him.

[Caius]

That really feels like blatant railroading. It seems like you're saying you want to follow a path or kill them if they don't. Please elaborate if that's not the case.