A split in the trunk of this strange tree reveals a swirling magical portal to an unknown destination.
Irminsul CR 17/MR 7
CN Gargantuan plant (extraplanar, mythic)
Init –2; Senses blindsight 120 ft., tremorsense 100 ft.; Perception +32
AC 33, touch 4, flat-footed 33 (–2 Dex, +29 natural, –4 size)
hp 301 (14d8+238); regeneration 10 (cold iron)
Fort +22, Ref +2, Will +15
DR 10/epic; Immune cold, sonic, plant traits; SR 25
Speed 10 ft.
Melee 4 slams +14 (5d6+12)
Space 20 ft.; Reach 20 ft.
Special Attacks mythic power (7/day, surge +1d10)
Spell-Like Abilities (CL 20th; concentration +26)
Constant—see alignmentUC (its own alignment only)
At will—telekinesis (DC 21)
Str 27, Dex 6, Con 32, Int 23, Wis 28, Cha 23
Base Atk +10; CMB +22; CMD 30 (can't be tripped)
Skills Bluff +12, Diplomacy +14, Intimidate +18, Knowledge (arcana, history) +9, Knowledge (nature) +14, Knowledge (planes) +18, Knowledge (religion) +16, Perception +32, Sense Motive +29, Spellcraft +20, Survival +17
Languages Common, Druidic, Elven, Sylvan (can't speak any language); telepathy 100 ft.
SQ planar portal
Planar Portal (Su) Within the split of an irminsul's trunk swirls a large planar portal, a permanent gate that links one plane to another. An irminsul controls whether or not specific creatures can pass through its portal, which grants entrance to a specific location on the linked plane. Those attempting to breach a barred portal must succeed at a DC 26 Fortitude save or be ejected and teleported to a random location on the current plane. If the trespasser successfully saves, it takes 6d6 points of damage and is sickened for 1 minute. The DC for this save is Wisdom-based. Mythic characters can expend uses of mythic power to forcefully pass through the gate, lowering the DC of the saving throw by 5 for each use of mythic power expended in this fashion.
According to legend, primordial gods seeded the multiverse with the irminsuls, powerful and intelligent tree-like beings that bind all their worlds together by their roots. At one time, these beings were plentiful, and prized for their knowledge and mystic properties. But powerful creatures hacked them to the ground because they believed irminsuls' wood had special qualities or sought to protect themselves from whatever lay beyond the strange portals.
Every irminsul is bound to a specific plane. The bound plane determines the creature's alignment, the nature of its regeneration, and the languages it knows. Sometimes irminsuls have special abilities based on the planes they are linked to. The sample irminsul is bound to the primal land of fey.