There are 4 Monolith bosses for the Yule 2015 event. They come in 5* and 6* difficulties. The 5* Obelisks drop one item, and the 6* Monoliths drop 3 items. The level 60 monolith is in Lirs reach, south east of Castle. Level 110 monolith is in Fingals Cave, directly south of the camp. Level 160 monolith is in Carrowmore tunnels, east of the main camp. The level 210 monolith is in Lirs Reach, south of the stone ring.