Note: my changes here are to adapt the abilities of the creature to the RM rules, not to make new/special rules. Also, remember that in RM it is more about the attack/skill/RR/maneuver/etc. roll than having a special abiiity that will negate the roll. (Such as Magic Resistance and Legendary Resistance.)
Tarrasque
Level: 100
Base Rate: 200 Spt/0
MS: MD
AQ:FA
Size: H
Crit: SL@
Hits: 3000H
AT: 20
DB: 60
OB: 350HBi
OB2: 300HCl X 2
OB3: 400HBa
OB4: 350HHo
Encounter: 1
Treasure Type: zzzz
Bonus Exp: Lx3
Outlook: Mean as hell
IQ: Low
The only things I would change here are the Speed (it should only be a little faster than your normal humanoid, so say around 70-80) and the base DB and OBs. But these last two are personal preferences of mine when it comes to big-bads like the Tarrasque (or other huge monsters). The DB should be high to reflect the fact that most hits just bounce of their hide (i.e., "hit" but do no damage), and the OBs should be lower to reflect that big things hitting little things (like humans, elves, dwarves, etc.) is actually hard - BUT, when they do hit, it is really gonna suck with a 4x or 5x Concussion Hits and additional criticals (see below). Thinking about it, I don't think it needs 3000 Hits either, 1000-1200 would be more than enough. The biggest god created for Shadow World, a 210th level Fighter/Cleric has merely
960 Hits.
Legendary Resistance (3/Day). If the Tarrasque fails a (Resistance Roll) RR, it can choose to succeed instead.
Magic Resistance. The Tarrasque has a 50% chance to ignore spells and other magical effects outright.
As I mentioned above, I don't think special rules are the way to go here. I think these are better reflected with the Tarrasque having high RR bonuses than some special (and unique) capabilities. At 100th level it is already nigh-impossible to affect with, well just about anything that requires an RR. Example: the Tarrasque needs, what a -70 on an RR to resist the spells of a 20th level caster? (Not including any other modifiers, strictly level vs level.) Meaning they can fumble and still succeed.
Reflective Carapace: Any time the Tarrasque is targeted by a bolt spell, a line spell, or a spell that requires a ranged attack roll.
Roll a d6:
• On a 1 to 5, the Tarrasque is unaffected
• On a 6, the Tarrasque is unaffected, and the effect is reflected back at the caster as though it originated from the Tarrasque, turning the caster into the target
Unfortunately, this will have to be a special rule of some kind, but I would have it tied to the RR roll (so as to not make a separate roll and slow down the game). Much like how Weapon Breakage works if the spell caster rolls a double (11, 22, 33, 44, etc... but any double, in this case) on the d100 roll Resistance Roll, then the spell is reflected back at the caster exactly how it was at the Tarrasque, only it is now going against the caster's DB. This does make it less likely - 1-in-10 as opposed to 1-in-6 - but it is quite a powerful defense, so I feel this is OK. You can use the original roll or do a separate roll for the reflected attack.
Siege Monster. The Tarrasque deals 5x damage to objects and structures.
Having it always do a multiple of Concussion Hits damage, sort of takes care of this already. Now, you might be able to delve into the rules presented in
#5542 RMSS - Castles and Ruins to grant them some specific effects regarding structures, but I don't know how that would work out off the top of my head.
Actions
Multiattack. The Tarrasque can use its Frightful Presence. It then makes five attacks: one with its bite, two with its claws, one with its horns, and one with its tail. It can use its Swallow instead of its bite.
Huge Bite: Reach 10 ft., one target. If the target is a creature and any critical is obtained, it is grappled.
An escape attempt can be made the following round. It is an Extremely Hard Contortions, Wrestling or AG/AG/ST maneuver.
Until this grapple ends, the target is restrained (-100 to all actions), and the Tarrasque can't bite another target.
Claw: Reach 15 ft., one target.
Horns: Reach 10 ft., one target.
Tail: Reach 20 ft., one target. If the target is a creature and any critical is obtained the target must make an Extremely Hard dodge maneuver (either using Contortions, Ag/Ag/Qu, Tumbling, Acrobatics – whichever is greater) or be knocked prone.
Frightful Presence: Each creature of the Tarrasque's choice within 120 feet of it and aware of it must make an RR (Resistance Roll) vs Fear or become frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, with a -20 if the Tarrasque is within line of sight, ending the effect on itself on a success. If a creature's RR is successful or the effect ends for it, the creature is immune to the Tarrasque's Frightful Presence for the next 24 hours.
Swallow: The Tarrasque makes one bite attack against a Large or smaller creature it is grappling. If the attack results in a critical, the target takes the bite's damage, the target is swallowed, and the grapple ends. While swallowed, the creature is blinded and restrained (-50 to all physical actions, -100 to all perceptions), it has total cover against attacks and other effects outside the Tarrasque, and it takes an “E” acid critical at the start of the Tarrasque's turns. If the Tarrasque takes 100 damage or more on a single turn from a creature inside it, the Tarrasque must succeed on a RR vs. Constitution at the end of that turn or regurgitate all swallowed creatures, which fall prone in a space within 10 feet of the Tarrasque. If the Tarrasque dies, a swallowed creature is no longer restrained by it and can escape from the corpse by using 30 feet of movement, exiting prone.
I would not allow the Tarrasque 5 melee attacks. I would do it like so:
Attack % Chance this attack is used ExtraHuge Claw (2x) 50
Huge Claw + Huge Bite 25 << Huge Swallow (Grapple)
Huge Bite + Huge Tail Attack 25 << Huge Swallow (Grapple) + Unbalancing
These should be more than enough to make the monster hideously dangerous.
For the Garppling effect, just have the Tarrasque do a Grappling Critical in addition to other criticals (perhaps even +1 or +2 severity if the size difference is great, as it is between the creature and just about any humanoid being).
The tail can inflict an additional Unbalancing Critical (with the same possible increase in severity due to the target's size, if you like, as well as having them shoved back 5' per level of critical (i.e., an 'A' = 5', a 'B' = 10', a 'C' = 15', etc.).
For the Frightful Presence I would halve the Tarrasques level as the power level of the fear (i.e., those seeing the beast need to resist against a power level 50 fear, not 100), as otherwise it would be virtually impossible to resist. This should be used if you are going to actually use the Fear/Awe Attack Chart on pg. 163 of
Gamemaster Law. It is entirely possible (probable?) that the vast majority of the beings observing the monster will be paralyzed with fear (0% action) this way. If you have the Frightful Presence at the full level of the Tarrasque (100), it is likely that most will have heart attacks and die upon seeing the beast.
Legendary actions
The Tarrasque can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The Tarrasque regains spent legendary actions at the start of its turn.
Attack. The Tarrasque makes one claw attack or tail attack.
Move. The Tarrasque moves up to half its speed.
Chomp (Costs 2 Actions). The Tarrasque makes one bite attack or uses its Swallow.
These sorts of things are generally totally unnecessary in RM, a big nasty like the Tarrasque is going to be more than enough without them. If, you feel that it needs some sort of "one-shot" kill defense, give it Fate Points as presented in
ICE5809P- Channeling Companion (pg. 43). The suggested amount of 3 is likely enough.
