To summon him in survival mode, you need to place a normal Mallorn sapling on a dirt, grass or podzol block in Fangorn and right-click it with Gulduril (this can only be done if you have negative Fangorn alignment), creating a corrupt Mallorn sapling. You can also plant a corrupt sapling, if you manage to get it from somewhere else (you could steal or buy it from another player on the server for example). You don't need negative Fangorn alignment to plant it, neither for the summoning itself. You should do this in or close to Fangorn forest, as you need some Ents nearby for the next step.
Then, some Ents will appear next to it and try to cure the corrupted sapling. Three Ents have to be killed in order for the Mallorn Ent boss to spawn. Keep in mind that the Ents must attempt to heal the sapling in order to count towards the summoning. Upon being summoned, he will say something like "Who dares challenge the might of Laurelindorenan!" (An old high-elvish name given to Lothlórien by the Noldor.)
In creative mode, you can plant a corrupted sapling and use spawn eggs for the three Ents or the boss can be summoned using the command:
Once you summon it, a purple health bar similar to the Ender Dragon's appears at the top of the screen.
The Mallorn can summon ents and huorns, and can also send a whirlwind of leaves towards evil players and NPC's. It can jump considerably high, and heal by "absorbing" the essence of trees, so choose a clearing or chop down some trees before summoning him, to deprive him of this ability.
After emptying its health bar for the first time, it will say a phrase, along the lines of "O Kementari, hear me! Strengthen me against the iron-bite of this little orc!" (Kementari is a name for Yavanna, the creator of the Ents, her more common name may also be used.) It will then commence to glow green and gain what seems to be infinite health. At this stage, fire is the only way to hurt it, as it seems immune to any pure physical damage.
However, to kill it, you'll need fire to weaken him and do significant damage, and it is recommended to use an axe during a fight instead of a sword, which even if it has more attack damage won't deal as much damage as it does the axe to him. The player should always bring something to set him on fire, as flint and steel, sulphur matches or lava, but the most useful items are modified weapons, like infernal on a bow or axe, with other modifiers to deal even more damage. Therefore the Mithril axe or battleaxe with the infernal modifier (and legendary) or a bow with infernal and fierce, are the best weapons to fight the Mallorn Ent boss. You also should consider to wear some decent armour and to have some magical drinks to heal yourself. For the end of the bossfight you'll need one or more stacks Rhûnic Firepots.
If you have more than +1000 Fangorn alignment, you'll lose 1000 by killing him, otherwise your positive Fangorn alignment will be set to zero. If you've got negative alignment in advance, you'll lose another 50 points.
|The Trees of Fangorn Forest|