After events unfold in the temple, you can make use of what you obtained there.

Requirements

This quest is available if you have completed the quest Legend of the Not-so-hidden Temple.

Starting the Quest

Talk to Almet in the Rak'tika Greatwood to begin the quest. There will be a cutscene.

Speak with Urianger

Go southeast to the Aetheryte plaza and go east down the stairs to reach the quest icon on the map. Talk to Urianger to proceed.

Use the Antidote

Dismount and target Runar, and then you can either examine or target him and use the Bottle of Antidote on him from the Key Items section of your inventory, or you can target him and use the icon to the right of the quest name in your list of active quests.

Offer Runar a Second Dose

Check on Runar to proceed.

Offer Runar a Third Dose

Check on Runar to proceed.

Speak with Urianger Again

Talk to Urianger to complete the quest.

Next Main Scenario Quest

After you complete the quest, talk to Urianger to accept the next quest: In Good Faith. There will be a cutscene.