"Life cannot be leeched from this monster" rare monster mod - can't leech mana either.

It states "Life cannot be leeched" rare monster mod but mana could not be either.
All other monsters in map gave mana leech, so no it was not a map mod.

Details:
League: Phrecia 2.0
Base league: Keepers
Ascendancy: Behemoth
Map: Mesa

Map mods:
none relevant to mana leech