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The idea is interesting. As the author said, the basis should be the opening of gates, and all creatures should have an ability similar to that of demons, so that it only affects them.
Regarding skills:
Make the creature invisible when using the ability (like demons).
At the same time:
1st level of ability:
1-5 tiers for 1 turn;
2nd level of ability:
1-7 tiers for 2 turns;
3rd level:
1-7 tiers for 3 turns;
4th level:
1-7 tiers for 4 turns;
and the super ability will add another 2-3 turns, or some other ability.
In any case, I imagine it like this.