The Mummy is finally available on some newer servers such as those on the Kongregate site. The following is first impressions on the character taken after playing it for a little while during October 2014.
The Mummy appears to have a Damage over Time (DoT) focus. A number of his skills inflict Poison and Burn, and the Poison ones can damage/prevent regeneration while also usually targeting the Front showing an intention for him to be a forward tank-buster.
The Mummy is also able to summon an additional minion to the field in a separate slot, similar to the Samurai Swords or the Cyclops rock totems. Through the various levels he gains access to an initial general fighter with some AoE capability, a heavy front Physical fighter, a healer and a Magic fighter. He also has some passive abilities that can boost the effectiveness of this summoned minion, including boosting the chance to have it strike twice during a round. The relative power of this summoned minion is supposed to be based off of a percentage of the Mummy's own stats, which means in theory it could become more powerful than any of your main Servitors although you can't load Bloodlines/Bloodline attacks on it.
The Mummy does not appear to have much in the way of defensive boosts and most attacks will hit the Mummy before/as well as the extra minion, so even with the extra team member the Mummy could end up getting overwhelmed at the higher levels once both sides have all 7 main servitor slots filled. It remains to be seen how effective this class is compared to the others.