Talk to Lahrian to discover his predicament and how you can help.
The 'hardest' part of this scavenger hunt tends to be the wild boar tusks. Kobold Stone Throwers drop the hearts you need - you can find plenty near the Golden Coast Resurrection Monument, or on the trail to the Forgotten Gardens/Seraphim Valley.
Plenty of earth elementals can also be found in the Seraphim Valley. Head as though you were going towards the Forgotten Gardens, but at the cave turn right (Northwest) and follow the path around past the monastery. Keep going until you cross over a bridge; there should be more than enough earth elementals in this area (along with Kobolds and wolves).
Once you have your hearts and stones (and with a bit of luck a few tusks), head back to the Resurrection Monument. At this point it's probably easiest to rely on your quest indicator for the precise locations of the remaining wild boar you need. There are usually a few on the high ground North of Lahrian's house.
When you have everything, return to Lahrian for your reward.
Note: Although you have to complete the quest Lahrian is Missing in order to access this quest, the two quests are not part of a chain (according to the quest log).