this is a bit difficult without scripts
actually it's easy but not very realistic.
here is the event way (until tsu or anyone else can make/find such a thing for you)
make a status called "taunted" and another inflicting "tauting"
they will both disable all actions (under restrictions in the status effect menu)
now, make them both unrecoverable
now back to the skill we will call it taunt (duh...)
make it do no damage at all, cost whatever mana (aka sp).
now link it to a common event.
in the common event do
variable taunt = (1,10) (or something)
now say you want 60% then
if taunt =>6 then
-loop
--message: the monsters are getting annoyed, select which one you wish to taunt.
--show choices (1,2,3,more)
---if 1 then
----if monster 1 is present then
-----inflict status (monster1) + taunted
-----end loop
----else
-----message: moron monster 1 isn't even here
---if 2 then
----same as monster 1 and so on until you get to the more part, then you put 4.5,6,more and later 7,8.
-repeat (the "finish line" of the loop)
-inflict status (hero- make sure you make 1 event for each hero otherwise it can go weird, simply copy paste the event, change this line and link each to it's respective hero skill tree) = taunting
now inside battle event you do "trigger event for turn 0+0X" (will work every turn)
if hero 1 is inflicted with taunting then
-deal damage (your call here): hero1
(same with the rest of the heroes)
you can also make it so that both stats will heal at the same time so it won't last forever but make sure they are removed at the same turn.
hope it helped, it isn't a very good system, but that's what you can do without scripts
i might be missing something but oh well