Is it just me or are we going to have a lot of questions about this team in the near future? Well, I'll get the ball rolling now!
If I mc an enemy mcer to do damage to a mystic, who takes the damage for the mystic retaliation? I assume it would be the fig that actually attacked and not anyone further back in the mc chain.
Also, the mystic ability is only good against directed attacks ala impervious? It seems to read so:
By attack, does this include pulse wave, splash damage, and poison? And does the retaliation occur if the mystic fig is KOed by the attack?

poison is not an attack, so it would not happen then. pulse wave and splash are damage from attacks, and would trigger the mystic team ability.

If the mystic is KO'd, they still took damage, and the team ability would still kick in before they died.

The MCed figure who attacked the Mystic would receive the damage.

There are two criteria for the Mystics ability---the figure must be hit by an attack and must receive damage. So taking an example from Super Senses, which shares that first requirement, we can come up with this---the Mystics ability will activate when a successful comparison against the figure's defense results in damage (push damage doesn't count). There are kinks to work out a la defense abilities and simultaneous sources of damage, but for the most part just follow that rule and you'll be fine.