a given Hero cannot stack both the Legendary and Mythic Effects (you can change if you want, but when the second one is set, the first one is lost) the new blessings can only be used once, like the previous ones.

in addition, Do legendary effects stack Feh?

Legendary or Mythic Heroes do not receive the effects of being in the same team as another Legendary or Mythic Hero with the same Blessing. The effects will only be granted to normal units that have been blessed.

Also, Do mythic boosts stack?

There will be a more common lower power version of the mythic effect and a rare chaser level that has a bit more power. The Mythic bonuses from each slot stack with one another.

in the same way Do visible buffs stack Feh? Visible buffs will not stack with other Visible buffs. Invisible buffs can stack with other invisible buffs and a visible buff. for example. If you have a flier next to two fliers with Hone Fliers, that unit between them will still get the flat +6 to atk and spd.

What does each blessing do Feh?

Each blessing can be conferred once only, so they cannot be removed and given to another Hero afterward. If you give a blessing to a Hero that has received a blessing in the past, the previous blessing will be overwritten. Blessings have two effects: Blessed allies receive double the usual amount of SP.

Do damage reduction skills stack in Feh?

It stacks, but multiplicatively. So you get diminishing returns as you go.

Do mythic bonuses stack DDO?

Mythic bonuses does stack with the same mythic bonus from other items.