Creating a Sand Soldier with Emperor's Dais gives plus 1 to another unit using Rengar's Legend?

Yes, creating a Sand Soldier token with Emperor's Dais will trigger your Pridestalker (Rengar) legend ability, allowing you to give +1 Might to another unit.

Why this works:

1. Playing a Token: According to RiftJudge FAQ #10901, when Emperor's Dais instructs you to "play a 2 [S] Sand Soldier unit token," this action satisfies the condition for "When you play a unit" abilities. Even though tokens are not Main Deck cards, they are units that are played.
2. Trigger Condition: Your Pridestalker legend ability states: "When you play a unit, give a unit +1 [S] this turn." Since playing the Sand Soldier token qualifies as playing a unit, the legend ability triggers.
3. Targeting: As established in RiftJudge FAQ #9769, you can choose any unit on the board as the target for this +1 Might bonus. You are not required to give it to the Sand Soldier token itself; you may choose another friendly unit to receive the bonus.

Sequence:

1. Conquer/Dais Ability: You activate the Emperor's Dais ability on the chain. You pay the cost and return your unit to your hand.
2. Resolution: The Emperor's Dais ability resolves, and you play the Sand Soldier unit token to the battlefield.
3. Trigger: Because you just "played a unit," your Pridestalker legend ability triggers and is placed on the chain.
4. Resolve Legend Ability: When the Pridestalker trigger resolves, you target a unit (other than the Sand Soldier, if you wish) to grant it +1 Might this turn.