Remember that a little bit before you left, they added Greater Dragons to the game, and if you were used to the regular ones, the greaters can clean your clock.
A few things that have changed/been added.
1. High Seas - a number of additional ocean encounters, including pirates and merchants (the merchants are a better source of high end ingots than spending the same time mining). IT also comes with a 20% storage boost.
2. Major Treasure Hunter revision. The new level 2s are equivalent to the old level 3s, the new level 3s are the old 4/5. No mining needed, dig distance based on Cart (so better to keep both LP and cart on character), and remove trap used to start the post-dig process (can do it with 0 skill, but still have to start it with the skill gump). Luckily RT doesn't require Detect Hidden anymore.
3. Major Taming changes: Tamers can train pets, increasing many of them to 5 slots, buffing resists & stats, adding more abilities, and using powerscrolls on them.
4. Time of Legends added skill masteries for many combat skills - not just the bard skills - but gaining masteries for the others require things dropped in champs (including the non-fel ones)
5. Reforging is Runic Crafting on steroids - uses Imbuing skill, targeting already-made normal base metal items, and consumes multiple charges off a runic. You get some category control on the crafting, and some desirable properties only come from lower runics. But you can get overcapped stuff.
6. If you get HS and the other storage boosts, your house will have 60% more capacity, and each bank box can hold 175 items.
7. There's now a dragon Turtle champ, and Barracoon is now just known as "The Piper", after people finally realized 20 years into the game the origin of the word (in addition to the potentially offensive contraction for him people used).
8. There's a Trammel Khaldun, with its own special champion-like fight.
9. The Ilshenar Garg city is gone, and in its place the Exodu super-champ.
And that's just the start of it.