Any known monsters we haven’t seen?

Fat dathrasi.

Sea Dragons: I think they refer to them a cetes somewhere. Also we haven't yet encountered a Great Dragon in game.

Genitivi says there are legends of flying chimera and wingless dragons in the jungles of the Donarks.

Unicorns - they may be rare or extinct but Dorian could hardly compare you to one if they weren't known in the game world.

Dracolisks that breath ice or fire, apparently bred by the current Archon's family (so there is a good chance we will get to see these) - Or has there already been the possibility of one as a mount?

Hope Spirits - previously we were told these were the most powerful of benign spirits but rarely encountered. Could do with one of them on our side against Solas.

It's a codex entry on demonic possession.

Hunger demon abominations tend to be cannibals or vampires.

Imshael was a desire demon, wasn't he?

Well I felt no desire so he failed.

Fex, the race that lived in Par Vollen before the Qunari arrived. Might not be canon, only mentioned by David Gaider once.

Scaled Ones, a race of serpent-like beings rumored to live in the Deep Roads. Potential progenitor to the Qunari, or some relation to the Old Gods.

Firesprites, a fae-like race mentioned in the Dragon Age Tabletop game.

There's supposed to be one group of Firesprites still in the Brecilian Forest.

I don't know why but listening to this description made me think of Thor/ Chris Hemsworth.  

Though I suppose Jason Mamoa might also work.

Like always, DA fans fall into the trap of thinking that just because a thing exists, it exists to please them.

Desire demons are still demons. Every time one has been encountered during the course of Dragon Age, it has tried to kill you or possess someone else. They've struck bargains, but only when doing so would benefit the demon.

It appears to be a human constant. Whenever sex enters the picture, sanity flies out of the window.