Corrupt Mallorn Sapling

The Corrupt Mallorn Sapling is a block created by poisoning a Mallorn sapling with Gulduril. Its main purpose is to summon the Mallorn Ent boss.

Obtaining
Players with negative Fangorn alignment can create a corrupt sapling by placing a Mallorn sapling and right-clicking it with a Gulduril crystal. This does not need to be done in the Fangorn biome.

If broken, it drops the uncorrupted Mallorn (unless a tool with the Silk Touch enchantment is used). Therefore it is advisable to bring along a stack of Gulduril crystals in case the sapling needs to be moved at all.

Use
When the sapling is placed, nearby Ents will come and try to heal it. If it has been placed in Fangorn and there are no Ents nearby then the sapling will trigger the spawning of some. This does not happen instantly; it may take some time.

When three Ents who began healing the sapling have been slain, the Mallorn Ent will rise out of the ground to avenge its Mallorn kin.