At level 10, you will get a spell, Drain Soul. If a enemy that is worth experience or honor is killed while you are casting that spell, the game will drop a soul shard in your bag. You won''t need one until you get to level 10 and gain the first pet that requires a soul shard, the void walker.
1. healthstones-stones that heal you and are on a different cooldown than potions
2. spell and fire stones-each have thier own uses-basicly helps you with more crit and spell stones can remove status from you.
3. soulstone- when used on a player will allow a dead player the ability to rez on the spot and not in a graveyard.
4. Spells- some spells need a shard to use
so shards are the lifeblood of a warlock-the imp is the only demon you'll get that doesn't need a shard.
when you get higher in levels and start doing instances its a good idea to bring lots of shards to make healthstones that you can pass out to your group.