Ye Olde Inn

Basic monsters end being a joke very quickly, mostly because their low BP compared with most of new monsters from expansions.

Getting the idea from the APP of advanced skeletons (can attack diagonally) anr goblins (can move and attack and continue moving) it would be cool to have the same for the other monsters. As a kid I used Battlemaster goblins and orcs as armored and gave them 2BP. So, something like that.

Advanced Dread warriors would be Doom guards (+1 MOV, +2 DEF).
Advanced gargoyles would be Guardians, +2BP and Inmune to magic , like the one in Kellars keep.

Advanced zombies and mummies could have +1 attack and defense or Regeneration, they defend from all skulls with just 1 Black Shield, so they are quite hard to destroy.

Advanced abominations should have frenzy, they add +1 attack and defense if they are below its full Body points.

Any more ideas?

The App also allows you to increase monster stats across the board:

+1 attack
+1 defend
+1 BP
+1 MP
(double wandering monsters)

Other ideas:

stone Gargoyles and Chaos Warriors (extra BP/defense)
"fiery" monsters (possessing 1 or more fire spells)
"ghostly" monsters (might have some powers of the specters such as passing through walls/enemies, channel dread)
ranged monsters... (who might have 1 attack in melee, or maybe their full attack. maybe 1 black die) orcs, goblins, skeletons with 2-4 attack dice at range
regenerating Undead (kill them and there's a chance they can revive with a die roll, unless killed by fire or holy water)
any monster that dies... has chance to "rise" as an undead (dice roll)
Orc or Abomination killed... splits into two goblins!
"boss" monster... has boosted stats and as long as he's alive, other monsters around him get attack/defense boost

Elite monsters: attack with black dice, defend with blue dice

any monster can become diagonal attack and/or ranged. The ATOH way of doing ranged monsters is kinda cool but having a dagger (1 die) attack close range seems a bit too weak, so I'd give them either regular attack at close range or else 1 black die (greater chance of skull).

Now if you want really powerful monsters... how about a 2 BP monster that requires you do two damage in a single attack (otherwise it heals the lost BP in time for the next character turn)? Or the Dark Company idea where 1 black shield rolled by the monster blocks ALL skulls?

I've been working a little here:
Advanced orcs: +1BP
Advanced abominations: +1 BP
Advanced Gargoyle: +1 Attack and +1BP
Armored skeletons (I got 4 Hasbropulse armored skeletons and wanted to give them some use): +2 BP
Advanced zombie: + 1 attack and defense
Advanced mummy: +1 Attack

There are plenty of suggestions for "Advanced Monsters" in various places on this forum, but I think that if you look at the full range of monsters in "Classic" HeroQuest (the 1989 edition) there are a lot more than you think. It is easy to assume that there are just the 8 original monsters (the ones that you get Monster Cards for in the box - I assume for cost reasons they didn't include more Monster Cards in the expansions), but a little research into the expansions and a bit of lateral thinking and there are plenty more official ones before you even consider homebrew

The Monster Mash