[Fantomen]

Depends on what the total mr adds up to. Some thugs have a high base mr of 15-18 or somesuch, in which case there are no way to "reliably" penetrate it. But you may have a decent chance with that communion, mind burn is inferior to soul slay though.

Sometimes it is better to have many mages spam the spell hoping some get through, rather than trying to boost a single mage to cast it a few times. it depends.