If I move Irelia Fervant to a battlefield and I have Mask of Foresight, will she gain 2 Might due to Mask & Unit ability?

No, Irelia, Fervent will not gain +2 Might in this scenario. She will only gain +1 Might from the Mask of Foresight, and she will not trigger her own ability.

Here is the breakdown of why this happens:

1. Mask of Foresight's Effect

According to RiftJudge FAQ #10619 and #5224, Mask of Foresight does not target the unit it buffs. Its effect is automatic when the trigger condition ("when a friendly unit attacks or defends alone") is met. Because Mask of Foresight does not "choose" or "ready" the unit (it is an automatic game effect), it does not satisfy the trigger condition for Irelia, Fervent.

2. Irelia, Fervent's Ability

Irelia’s ability reads: "When you choose or ready me, give me +1 [S] this turn." As established by RiftJudge FAQ #5224, this ability specifically requires "you" (the player) to be the one performing the action of choosing or readying her. Because Mask of Foresight is an automatic buff and not a player choice, it does not trigger Irelia's ability.

Summary

• Mask of Foresight: Triggers (assuming Irelia is attacking/defending alone) and grants her +1 Might.
• Irelia, Fervent: Does not trigger because the +1 Might from Mask of Foresight is not a player-initiated "choose" or "ready" action.
• Total: +1 Might.

This is my interpretation based on the mechanics of triggered abilities and player choice as defined in the provided FAQs. No official FAQ exists for this specific combination, but the interactions with Mask of Foresight are well-documented.