[Sticky] 20-30 in 24 hours (Guide)

20-30 quick leveling routine (7 hours)
(20% xp pot) *Not Required but helps.

1. collect heroic sagas at 20 (Saltmarsh, Feywild, Isle of Dread, Ravenloft, Gianthold, Sharn, Cogs, etc.)

2. Legendary Saltmarsh slayers - have at least 4 members in group for max spawns, preferrably 6 for max kills.  Rare chests have sentient xp, star and nebula fragments.  Video: A Tour of Saltmarsh Rares
3000 slayers in 15-30 minutes (200% slayer pot)
Level 22

3. Legendary Feywild Slayers - have at least 4 members in group for max spawns, preferrably 6 for max kills.
3000 slayers in 15-30 minutes (you can cap both Saltmarsh and Feywild with one 200% slayer pot)

Level 23 (1 hour total)

4. Zerg R1 epic leveling dailies for first time xp

• Lords of Dust chain, Spies in the House, Offering of Blood (max level 25 for delving bonus)
• Wiz King, VON 3-6 (max level 26 for delving bonus)
• Epic Crucible (max 28 for delving bonus)
• Epic 2-Toed Tobias (max level 29 for delving bonus)
• Epic Deleras part 4 (need opener), What Goes Up (need opener) (no max level for delving bonus)
• Other big epic xp quests include Through a Mirror Darkly (no max level for delving bonus)

3 hours
Level 26 (4 hours total)

6. Epic Orchard Slayers (200% slayer pot)
7500 kills in 30 minutes to an hour - have at least 4 members in group for max spawns, preferrably 6 for max kills.
Level 28 (5 hours total)

7. Barovia Slayers (200% slayer pot)
Split up and be sure someone is doing the downhill run from Amber Temple ddoor at bottom of the hill, mobs will have respawn by then- have at least 4 members in group for max spawns, preferably 6 for max kills.

7500 kills in 30 minutes to an hour

level 30 (6-7 hours total)

If you are not level 30 yet you can do Thunderholme Slayers if you like (with 200% slayer pot) or start legendary reaper questing.
7500 kills in 1 hour - have at least 6-8? members in group for max spawns

Once you are at cap, I recommend doing as many first time legendary reaper quests as possible for big first time reaper xp.  More about legendary reaper questing here.