Call Help - The monster calls for help. If successful, a new monster joins the fight. If unsuccessful, the monster's turn is wasted. The listed monster is what we've seen appear.
Howl/Frighten - A hard to resist move that prevents the target for taking action for 1 turn. It is resisted by NUMB resistance. It can only be applied to a player/monster once per battle.
2-Hit - If physically attacking, the monster/player attacks twice. The targets can be different or the same for each attack.
Boomerang - This is a group attack that deals 2/3 of the damage per target than the monster's single target attack.
Guard - Same as the defend command for players, this reduces damage taken by the monster by half.
Regen - If damaged, the monster recovers a fraction of it's max HP after its action each turn.
<status> Hit - A normal physical attack with a status effect adder. If the physical attack did 1 or more damage (ie. not dodged or failed), a resistance check for the appropriate effect is done. Even on a successful resist, the physical damage is still done.
Toxic Hit - This hit ability combines sleep and poison. They are resisted seperately.
Freeze Hit - This hit ability may just be a Sap Hit, with the same effect as Sap coupled with damage. Alternatively, it could be a anti-buff hit, that removes buffs applied on the target.
Att+, Def+ - Currently only found on boxslimes. It reaches inside itself & pulls out a weapon or shield, increasing either its attack or its defence by 5. It can only be used twice per battle.
Charge Up - Spends its turn charging up its physical attack. On the following turn, it can attack for double its usual ATT value.
Breath attacks hit all players (or foes, when used by a player). They can be resisted, but, currently, that is the only defence against these abilities.
Fire Breath - Deals 16-23 damage each to all targets.
Toxic Breath (Poison Breath) - Poisons all targets.
Sweet Breath (Sleep Breath) - Puts all targets to sleep.
Scorching Breath (Paralysis Breath) - Paralyzes (Numbs) all targets.
Infernal Breath (Stopspell Breath) - BURNS all targets. From its one use, this appears to be just a form of stopspell on all targets.
Change Form, Spawns Babbles, Lightning, BeDragon, Becomes Skeleton, Become Poltergeist, Possession, Tremors - You want to know what a boss will do ahead of time? Mwahahaha!