Currently, there are 17 underworld factions
You have to purchase the faction on your map, then finish the faction's Quest before you can start its Delve.
Delve as deep as you can in each faction with a full team of faction troops as you acquire them and upgrade them. Build your hoards. If you're able to max out 2 factions, you could get this. But most people will need to spread this out over several factions.
5000 divided by 17 = 294.11 per faction average renown. So it should be quite easy to get this achievement now.Renown Points Breakdown for each Faction:
Best Delve Defeated (max 500) X2 (max 1000)
Best Delve with no casualties (max 500) X1 (max 500)
Best Delve using the faction's team X1 (max 500)
Treasure Hoard level X5 (max 500)
Total points possible per faction: 2500
You need this^ achievement to get another achievement v