Guild Wars 2

you did not follow the story huh ?

you were in his brain the dragon itself is too powerful to fight directly

the whole ground you stand on is him the trees around you everything

Well because Mordremoth is the MIND Dragon. The jungle itself is him, he doesnt have a form like Zhaitan and the others. Actually the Elder Dragons are not traditional dragons, they are primordial forces of nature.
Lets just say, tomorrow our “Mother Nature” will take the shape of a Dragon. It would be a dragon, or the primordial force of nature.The example from above, is the answer to your question

lol he deleted the post ?

Spoilers for Heart of Thorns story and content below!

It’s actually confirmed in game (via Laranthir who has somewhat different dialogue in Dragon’s Stand depending on if you’ve completed HoT’s final story mission “Hearts and Minds” or not) that the Mouth of Mordremoth, the final boss of the Dragon’s Stand meta event chain, is the physical manifestation of Mordremoth. The Pact’s assault on the Mouth is distracting Mordremoth (as stated by Canach in the story mission and even implied with Mordremoth’s sylvari-only line “Armies cannot stop me”), which gives us a chance to enter Mordremoth’s mind to fight him simultaneously there. There are also other clues such as the Mouth’s shadowy visage being seen when we enter the Dream in the story (and during the battle against Mordremoth’s avatar) and the explosion in the story’s end cinematic being repeated at the end of the DS boss encounter when the Mouth suddenly suffers what looks like a stroke and dies.

For those curious about how the Mouth fight fits into lore if you’ve already completed “Hearts and Minds”, Laranthir’s dialogue changes after completing the story. As the Commander questions him about how the Mouth can still exist even though Mordremoth has already been slain, Laranthir explains that although Mordremoth’s mind is gone thanks to what the Commander did in the story, the Mouth still exists as a physical manifestation of the dragon’s hunger (this “mindless” nature is somewhat contradicted by the Mouth still talking to us as Mordremoth during the meta event battle, but this is likely story and gameplay segregation or else the Mouth is simply repeating those phrases on autopilot). The likely way the events unfolded could’ve thus been like this: the Pact fights against the Mouth and thus distracts the dragon while the Commander’s party fights the dragon’s avatar in the Dream. After destroying both the dragon’s Mind and Mouth more or less simultaneously (resulting in the explosion seen in the cinematics), the Mouth revives some time later and attacks once more, and the Pact defeats this manifestation of the dragon’s hunger again with the Commander’s help.

The Mouth of Mordremoth, being the physical manifestation of Mordremoth, does thus look like a dragon although it shares more features with dragons of eastern mythology than western mythology due to it being more worm-like and slender rather than the bulkier dragons western audiences are used to seeing.