Dragon Encounters

Making dnd combat fun, finding monsters that fit together, monster tactics and strategies, and other ways of using the monsters of dungeons and dragons

TYRANNASAURES REX: The Boss They Shouldn’t Defeat


Combat rating 10


1 Tyrannosaurus rex (CR 8)

4 griffins (CR 2)


Combat rating 11


1 Tyrannosaurus rex (CR 8)

1 Otyugh (CR 5)

1 Shambling mound (CR 5)


Combat rating 14


1 Tyrannosaurus rex (CR 8)

6 Elephants (CR 4)*

1-2 Giant constrictor snakes (CR 2)


* T rex induced stampede

Combat rating 16


1 Tyrannosaurus rex (CR 8)

2 Displacer beasts (CR 3)

1 Grick alpha (CR 7)

3 Wyverns(CR 6)

The tyrannosaurus rex is one of those rare monsters that will be exciting encounter just on the strength of their name, or reputation. With other monsters, there are various ways to make them exciting, but they won’t measure up to the reputation that the T. Rex already has. I can’t name ten monsters in the Monster Manual that can compare. 

The problem with running the T. rex as a big boss fight is that the T. rex’s stats are boring. It’s a straightforward melee fighter with no special tricks. Nor is it simple to add any, even if you’re into homebrewing. Most possible changes will leave it no longer feeling like a T. rex, thereby ruining the point of running one.

My solution? The players should only fight it when they’re at a level where they cannot possibly beat it. [If they’re at fifth level, you could consider adding a little to its HP, and maybe increasing its damage by a point or two. I’ve heard suggested that so long as you keep to the range of what it could actually roll, this doesn’t even count as homebrewing.]

Fighting it at such a disadvantageous position elevates it from a simple opponent to a force of nature that they can’t defeat, that they need to survive.

Setting the stage

When running any monster that you want to make into a boss, it is always worth establishing its presence and its reputation beforehand. In the case of the T. rex, its reputation doesn’t need establishing, but foreshadowing its presence can be worthwhile.

If the dungeon is short, only one or two sessions, I wouldn’t bother. The fact that there are dinosaurs around establishes its presence. Everybody knows that no one would run a dinosaur themed anything and leave out the big star. If your dungeon/quest is a long one, however, you might want to bring in occasional hints as to the T. rex’s presence, or your players will start to wonder why they’re not catching sight of it, despite being here all this time.

There are two types of signs, evidence of its passage, and sight of the monster itself. (Normally, there would be a third. NPCs letting players know about it. This one doesn’t fit a dinosaur dungeon, which doesn’t tend to have NPCs. It also doesn’t fit a T. rex, which doesn’t lend itself to having important information that the NPCs have to let the players know about.)

Evidence of its passage: Eggshells identifiable as broken T. rex eggs, tracks left in the mud, and hearing it roar in the distance are the best bet. Make certain to have the eggshells be in a place where it would make its nest, and the tracks be in a place where it makes sense that there would be mud.

Catching sight of the beast: Have them hear the earth shake, or the beast roar, and they have to hide to prevent it seeing them. Let them see it from a hill, [or from a treetop], and they need to decide if they can get past without it seeing them, or if it’s too risky, and they need to take the long way around [or equivalent thereof.] If they see it fighting, and demolishing, another monster or dinosaur, you can simultaneously establish its presence and build its reputation. Ideally, have it be demolishing an opponent that they already fought and found challenging.

Combat Encounter 1: 3-way Fight (difficulty varies)

One way to use the tyrannosaurus rex is to have it come and join in to a preexisting fight. If using villains, it could/should be a fight involving them, but you could also add it to a fight against a group of allosauruses, or any other type of monster. I would choose to use a group of villains or monsters, not one strong villain/monster. (There are multiple reasons, but the most compelling reason is that I would have the T. Rex be against both sides equally, and that’s very hard to achieve when one side contains only one individual.)

Let the fight go on for a few rounds [two should be plenty], and then bring in the T. rex at the beginning [initiative 20] of the following round. [Another advantage of multiple enemies is that you can have extra enemies waiting around the corner, ready to join in if the first batch get defeated too fast.]

While not absolutely necessary, it will be advantageous to have all the PCs be near the enemies, not to have the spellcasters be shooting from a distance. This can be achieved by having the villains/monsters originally ambush the PCs; by having the PCs stumble into the midst of their opponents unexpectedly [washed down the river, possibly on a boat; or stumbling/falling down the side of a mountain are obvious ways].

When using villains, this can also be achieved by having them be up to something that the players want to stop, such as digging up a treasure or casting a ritual spell. The villains carrying out the deed will be out of sight around the corner, thereby forcing the PCs to dive into the middle of the villains to get to the main target.

When the T. rex shows up, it will charge into the middle, attacking between both sides at random. [The fact that the T. rex has two separate attacks, which cannot both be used on the same target, will help a lot with this.] Presumably it will focus on the targets nearest to it, but you can easily get away with having it charge 15 feet in one direction, even though there is a target only 10 feet away in a different direction.

The one thing that you need to avoid is letting your players realize that you’ve got a pattern, whether it’s to always use one attack against each side or to balance who the T. rex attacks with how well your players are doing. I’m not saying not to do this, just not to let them realize that you’re doing it.

Last, but most important, the other enemies should react to the T. rex’s arrival. If they can break and run, they should do so. They can always fight the PCs again another time. If you want to keep them from fleeing, make it so that there is no easy way to leave the area, or so that there is only one easy entrance and it is where the T. rex is standing. Or you can have them flee, and let the T. rex give chase.

If they’re doing something that they really don’t want to flee from, such as digging up a treasure, you should still make sure to show them panicking. Have some of them flee, and describe the others as being white-faced and are mention their hands are shaking. Have the ones digging intensify their efforts and shout to their minions to just give them a little time. If they just continue fighting like normal, it will make the T. rex seem less powerful.

(For this reason, I would make certain not to use constructs or mindless undead. While there is no reason for them to flee, it still won’t make the T. rex look good.)

I wouldn’t have them fight against the T. rex, either. While futile defiance can be added to a scene without making the monster look weak, there is always a small chance that they’d weaken it enough for the players to kill it, and you really don’t want that.

Combat Encounter 2: To Avoid its Notice (difficulty 7)

Keeping in mind that the T. rex has to be significantly stronger than them, there are several scenarios that this could lead to.

One scenario is that they need to get something, but a T rex is prowling or sleeping nearby. On a simple level, this would be a skill check for the rogue, or the PC with the highest stealth. You can complicate it by placing the T rex to near to the objective, and or not providing enough cover, thereby forcing them to create a decoy.

If they try to take out the T. rex with an enchantment type spell [a spell that imposes a condition] the T. rex can hear them begin to chant, if the spell requires verbal casting, and they’ll have to either stop or roll initiative to see if they can finish before the T. rex attacks. [Because of the boss status that I want the T. rex to have, I would argue that the T. rex’s hearing and smell are too good for the hidden status of the PCs to slow it down, or to give it disadvantage.]

Another way to complicate it would be by shaping the wilderness around the object to obstruct the way. Loose branches, or dead thorns, either of which would make a noise when passed through. A small chasm which would need to be crossed, or putting the object high up on a nearby hillside. Or it can be partially covered by boulders from a landslide, or a fallen tree.

Regarding the nature of the object, you can of course use a potion ingredient that they have to collect, like in some of my previous articles. (If you do so, the reputation of the T. rex demands that it be the final and rarest of the ingredients.) If using villains, you can have one of them be lying dead, possibly killed by the T. rex, and holding an item that they’ve been trying to collect for a while.

Or, if seeking a treasure, the entrance to the final dungeon can be right past where the T. rex is. This option introduces the added complication of needing to get the entire party past the T. rex.

This entire combat encounter has a significant chance that it won’t result in battle. If you want, you could set it up so that the T. rex will only be fooled for so long. Let them know beforehand that the T. rex will smell the scent they left behind, and even in the best-case scenario will eventually pursue. I’m telling you to let them know beforehand, because that way getting a half-mile or so head-start will feel like a victory. If you don’t tell them, getting pursued at all will feel like a cheat.

A different form of the above scenario is to have them be cornered by the T. rex, and having to figure out an escape. Basically, they enter a narrow valley, ideally in order to gain something [so that the players don’t object when you tell them that they all entered a dead-end valley], and as they’re about to leave, the T. rex enters the valley after them. They have to find some way to get the T. rex out of the way so that they can escape.

The T. rex isn’t intelligent, which means that it can be tricked, or lured to one side. The small amount of room in the valley is what will make doing so challenging.

Combat Scenario 3: The Chase (difficulty 6)

The setup is simple. Something they do, most probably needing to go near or collect something from near the T. rex [although simple bad luck will also work] puts it on to them, and now they need to escape the area and get somewhere safe before the T. rex catches and kills them.

The ideal terrain for it to chase them through is terrain that they’ve already been through, and fought encounters in, thereby making it already familiar to them.  [This scenario will work especially well as the final encounter of the area, allowing them to revisit all/many of the places they’ve already been as part of their final bid to escape.]

If you want, you can combine this scenario with Combat Scenario 2 to give a stronger reason why the T. rex is attacking.

I am now going to list different terrains, and how they will favor the T. rex and/or the players.

  • Grassland: Allows the T. rex to move without them seeing. Hides its location. If they shook it off, allows it to show up from a different direction, and be near them without warning. Keep in mind that grassland does not need to be absolutely flat, and even a small difference in elevation can make a major difference in visibility.
  • Jungle: Same visibility issues as grassland, made worse by thicker foliage. Because it’s worse, there is also the possibility of the T. rex getting confused, which will buy them an extra 1-2 rounds, but might end with the T. rex showing up from any direction. Allows thorns and other obstacles that will block the PCs but not the T. rex. Allows climbing trees for safety, but the T. rex might batter at them until the PCs fall, if it spots them. Poor visibility for ranged attacks.
  • River: Slippery rocks, more likely to topple PCs than the T. rex, who has clawed feet. Allows the possibility of escape via destroying the bridge behind them, unless you decide to let the T. rex ford the river, either in their location or in a different one. Allows possibility of escape by boat, or holding onto logs.
  • Swamp: Slows down PC movement. Might cause T rex to abandon chase, temporarily or permanently, if it fears sinkholes.
  • Hills/mountain: Limited areas to move into, which means that PCs can get cornered, especially if the correct exit isn’t obvious. Allows the possibility of collapsing the rock behind them, or onto the T. rex, to buy time.

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About Me

I have been a DM for several years, and I was designing home RPG games since my young childhood. I have been a fan of many different types of games (computer, board, RPG, and more) and have designed several for my own entertainment. This is my first attempt to produce game content for a wider audience.