Tarlach's simple but meaningful gift to Kristell; a Black Rose.
Through the admission of Tarlach's book and even the relationship mechanic of the game itself, the native people of Erinn are stated to be incapable of remembering Milletians over a long period of time due to their different perceptions of time. However, it's gradually made clear throughout all that chapters that The Milletian's deeds allow them to leave a permanent, lasting impression upon people, which culminates in two conversations with Duncan and Aodhan. Both reminisce how they first met with The Milletian and the heroic acts that pertain to them. If the player responds to their stories with "I remember," they will respond with an equally assuring "Who could forget?"
As mentioned in tearjerkers, you're given the option of hugging Eirawen while the poor little girl is grieving the deaths of her father figure and assistant.