Build set of Gen 6
Ability – Sheer Force
Stats – HP (252), Attack (252), Special Defense/SpD (4)
Nature – Brave
Item – Life Orb
Move set – Dragon Claw (stab), Fire Punch, Iron Head/Gunk Shot, Protect
When it comes to dragons, it's one of the most favourite Pokemon types to use because of its sheer power and great defensive resistance. However, not many would consider using Druddigon due to its abysmal speed, nonetheless this thorny dragon has incredible 120 Attack stat. So in other words, its sole purpose is to kill everything it touches in Trick Room.
Strength
The only reason that you'd want to use Druddigon is for Sheer Force, combining it with Life Orb item, it could obliterate most Pokemon and not to mention, it has tons of moves at its disposal.
Druddigon’s other two ability Rough Skin and Mold Breaker are also good, a defensive build should make use of Rough Skin + Rocky Helmet and maximizing Defense to the max. Mold Breaker on the other hand is the "least" useful which can be used too I guess, but I sure won't want to waste that 120 Attack stat away.
Weakness
Being a pure Dragon-type, that makes it weak to Fairy, Ice and of course, Dragon. There's nothing much to say about its weakness, really, the defensive spread is good enough so it's quite a tough one to take down since HP stat is maxed.
Oh wait, Dragon Claw cannot be utilized by Sheer Force. Oh well.
Moveset
With the power of Sheer Force and Life Orb, it grants Fire Punch and Iron Head higher bonus power and it’s sure to go in for the kill immediately. Fire Punch is much needed to handle those steel type Pokemons, since Dragon Claw is weak against it. And Iron Head will decimate every single Fairy except Azumarill. Gunk Shot is also a worthy move to replace Iron Head to counter Fairy-type but its 80% accuracy says otherwise.
Other than that, it also has many other moves to benefit from Sheer Force + Life Orb combo, depending on what your team lacks it can also learn Crunch, Thunder Punch, Rock Slide and Sucker Punch (ok, I know this move doesn't gain anything but it's to compensate for being slow).
Closing thoughts
Indirectly, Druddigon is the physical embodiment of Dragalge and these are the only two Pokemon Dragons that can OHKO Sylveon easily. A Trick Room Druddigon should never be messed around as this build's sole purpose is to kill everything it touches, it did well in my Trick Room team but eventually it got replaced because I have a better Fire alternative (Mega Camerupt) compared to the boosted Fire Punch, as well as a stronger Dragon-type like Dragalge, but it's still a good Pokemon to use for Trick Room.
So Druddigon, I choose you! Glhf!