If this game gets ported to bedrock perhaps there should be mobs that move underground as well?
Ok honestly, regardless if this gets ported over to Bedrock or not, having underground mobs sounds really good, maybe silverfish (as they are pretty much very useless as of time of making this post).
If underground mobs happen, here is some suggestions that I have.
Underground mobs pros:
Cannot be attacked by player weapons
Some sword and bow abilities
Unable to be targeted by the following towers:
Archer Tower
Necromancer Tower lvl 1, lvl 2, and lvl 3 shulker path
Turret Tower
Zeus Tower
Sorcerer Tower
Mage Tower
Leech Tower (Partly)
Poison Tower
Underground mobs cons:
Ice Tower
Artillery Tower
Leech Tower (Partly)
Quake Tower
Low Health
Some sword and bow abilities
Im going to explain my reasoning for what I listed above.
Cannot be attacked by player weapons, for pretty obvious reasons, if mobs are underground, it is pretty hard to wack them with a weapon.
Some sword and bow abilities that won't have an effect is also pretty obvious, something like the shulker bullets from the bow or spikes and fire from the sword won't work, as (how I see it) is that shulker bullets don't go into the ground, and that spikes are embedded into the ground, which can be valtz around as it is just bumping into a not sharp part of the spike, and there isn't a lot of oxygen in the ground, so fire doesn't really work. On the flip side the Freeze and Quake on the sword works really well, and applies damage, and the same thing with the bazooka for the bow, but for the sniper I think it can go into the ground a bit doing damage if it hits a mob.
Most of the towers that won't do anything should mostly be obvious, arrows aren't really effective for mining for stuff. Iron Golems and shulker bullets from the necromancer can't do much, but if it is the snow man path, it can slow down and damage underground mobs due to the freezing nature. Sorcerer and Mage towers aren't viable in my opinion, as lightning from Zeus shouldn't be effective on the underground stuff, and the animals from the sorcerer towers have the same reason from necromancer iron golem deal. As I said before with the flame ability, mage towers can't ignite mobs underground due to the lack of air. The last thing is Leech Tower, but as I said, only partly, I dont believe the laser to charge up the tower can lock on, but when it sends the giant laser down the map should do damage against underground mobs. Artillery Towers uses explosives to do damage, which I believe should do damage against the ground troops, as it should "destroy" the ground (it doesn't actually destroy the ground on the map). Quake towers uses earth quakes to apply damage and stun, should be pretty obvious why it should do damage. Ice tower should not only slow down underground mobs, but also applies damage, regardless if it is lvl 4 or not (lvl 4 does damage).
The last thing I want to talk about is potions (AKA pots). Both of the offensive pots (regen and speed) should still work, and half of the defensive pots should work, as the slowness one should be obvious, its the same as Ice Tower, but doesn't apply damage, and lava pots replaces the ground to lava for a bit of time. Meteor pots should slightly work, with reduced damage but not completely immune, and for Zeus pots just doesn't work because lightning stops when it hits ground.
That should be all, sorry for the wall of text, but this should give my complete opinion on underground mobs. Just a thought though, of course feel free to provide your opinion about what I said, if you agree or not, and if you dont, I would love to hear why (if you aren't rude about it)