One of the holy items is in Verdistis, the other in the Dark Forest.
Gathering the Holy Items and the Sacrifice

When you exit Iona's dungeon, Arhu the cat will approach you and give you a quest to rescue Zandalor. Do so (<span class='standouttext'>Spoiler : </span><span class='spoiler'>Rivertown sewers treasure room entrance</span>) and let him teleport you somewhere, then clear that smallish area to find the imp who 'borrowed' your teleporter stones.