Incense is an item that can be purchased from the cash shop or acquired through ingame methods.
It calls upon your patron, increases your immunity to Control effects, significantly increases HP and MP (it also used to grant immunity to the Fear of Death effect, until FoD was removed from the game).
The martyr's blessing is very powerful and gives players great advantages both in PvE and PvP, but beware, it's duration will count down even when you are offline, so it may dissapear even if you are not playing at that time!
Learn more about Patronage and Blessings.
This is an example of a patron's blessing and a screenshot of the Incense description and cost:
In the picture you may see that a Small Cone of Incense costs 20 boutique coins. This Cone increases the duration of your patron's blessing by 1 day, but there is also a Large Cone of Incense that costs 260 boutique coins and extends it's duration by 21 days (3 weeks) and saves 160 boutique coins (since it would cost 420 boutique coins to get the same effect when buying the small cones of incense).