In the inheritance, Renduldu simply stated that Mahira Tusk's actions helped form his mind faster. He didn't care about what she had done to him, since before that, he didn't have sentience. The influence from his Silver Grade Secondary Nature had already destroyed whatever intelligence he had long ago.
It was a necessary process he had to go through to become a Mystic Empyrean Tentacle. As a result, Renduldu didn't blame Mahira Tusk. Instead, he honoured her actions. After all, without her, he would have either died or been consumed by the other two Empyrean Tentacle variants.
It was only thanks to Mahira Tusk's support that an Iron Empyrean Tentacle reached Mystic Grade. Moreover, depending on their birth variant, and the order of variants they consumed, the power they could unleash—through the harmonisation of their three Natures—upon becoming a Mystic Empyrean Tentacle varies.