We've got some Orc Raids among Tibia, but only from huge raid near Thais gates and on Fermor Hills you can loot Amazon Set.
The first one is announced:
0.00: Orc activity near Thais reported! Beware!
00.04 [-]
00.07: Thais is under attack!
00.09: [last wave with Orc Warlords)
Raid on fermor Hills is unannounced.
Both are once a month, but exact time is random.
Unannounced raid near Thais Lighthouse works in a completely different way and there is no chance to loot there any part from Amazon set. It appears once per week.