On top of being a new completionist cape requirement (as replacement for the 500 killcount requirement), I have the following rewards in mind:
PvM rewards (for Ironman mode players: upon completing 14/27 achievements):
- All bone drops are automatically noted
- WildyWyrm clue scroll has 'teleport' option which teleports you to a random WW (only works up to lvl 20 wild)
- Piles in the resource area notes your items for free (so he doesn't take 1 item as fee)
- 20% discount on all items in the Bounty Hunter store
- Player kills always have a small chance to drop an elite clue scroll, higher chance when killing BH targets
- Artifact drops will always give one of the 10 most valuable ones (out of the 17 artifacts there are)
- Teleport spells are free in combat, no runes or teletab required (also applies out of wild)
- Ancient obelisks give you the option to choose which obelisk to teleport to
- Degradeable items last 30% longer in the wilderness (applies to hybrid armour as well)