UPDATE (12-May-16): A Delver Class Summary is now available.
A delver class for human characters. (Adapted from the ACKS Dwarven Delver, they have the Thievery skills that I like in a PC, plus d6 HD. Note, however, that they lack Backstab, Pick Locks, and Remove Traps.)
HD 1 (d6), Fighting 1b, Thievery 2.
Base XP: 500 + 500 + 400 = 1400 for 2nd level.
2 Fighting Styles: Two-weapon style; two-handed weapons.
Broad Weapon Selection: One-handed melee weapons, all missile weapons.
Narrow Armour Selection: Leather armour or lighter (no shields).
Thievery Skills: Detect Traps (see below), Move Silently, Hide in Shadows, Climb Walls.
Custom Power: Alertness @ 1st.
Maximum Level: 14th.
Prime Requisite: Dexterity.
Requirements: DEX 9.
Proficiencies: As Dwarven Delver; plus Cat Burglary; minus Engineering, Goblin-Slaying, Mountaineering, and Siege Engineering.
Attack Throws: As Thief.
Saving Throws: As Thief.
Magic Items: As Thief.
Stronghold: Hideout (as Thief).
Detect Traps: Because of their experience underground, Delvers may detect traps, false walls, hidden construction, and notice if passages are sloped with a proficiency throw of 14+ on 1d20. (As per ACKS Dwarf; note that this does not include trap removal.)
Character Class Templates: As Dwarven Delver, except replace Mountaineer with Caver (Caving & Mapping proficiencies instead of Mountaineering & Endurance).