This upgrade allows Obyn to spawn up to two more wolf spirits (four more with the Level 2 version). By default, he passively spawns a wolf spirit every 2 seconds until he reaches the maximum, but when crosspathed with Spirits of the Forest, he cannot spawn these wolf spirits passively and can only spawn them by howling.
Empower glades by staying in them, increasing their size and XP dropped.
This upgrade allows Obyn to grow a Sacred Glade by standing on it, increasing its radius by 20% per second (40% per second with the Level 2 version), though it shrinks back to its normal size over time if Obyn stops standing on it. Once a Sacred Glade reaches double the radius, it becomes Empowered and remains at that size until it expires. Empowered glades cause Bloons to drop one extra XP orb when popped, which they still auto-collect as normal.
Obyn can only grow one Sacred Glade at a time; if he stands on multiple overlapping glades at the same time, none of them grow or shrink. Once a Sacred Glade is Empowered, he cannot grow any other glades until it expires.
Empowered glades convert collected XP into healing bananas.
This upgrade causes each fully empowered Sacred Glade to spawn a banana collectable once for every 3,000 XP it collects (2,400 XP with the Level 2 version). Once a Sacred Glade generates a banana, it will not generate any more until the player collects it. Despite what the description implies, the XP it collects still goes towards the player; it does not "convert" the XP into bananas.
Howling while in an empowered glade summons another Wolf Spirit.
This upgrade causes Obyn to summon another wolf spirit every time he uses his howl attack from Leader of the Pack while a Sacred Glade is fully empowered, and raises the maximum number of wolf spirits Obyn can have at a time by 5 (to a total of 6 by default, or 8 with Pack Tactics, or 10 with the Level 2 version of Pack Tactics).