User blog comment:Emlightened/Early Birthday Present For Deedlit/@comment-5529393-20170730212008/@comment-5029411-20170731111056

Regular cardinals are collapsible, but non-regular cardinals aren't. Take the example of $$\Omega_{\omega}$$, they aren't collapsible. Therefore, $$\psi_{\Omega_{\omega}}$$ shouldn't be exist.

$$M_{\alpha}$$ for all $$\alpha$$ < $$\omega$$ aren't regular, but they are regular Mahlo cardinals. But $$M_{\omega}$$ isn't and not collapsible.

So $$M_{\omega}$$ might be reduce, not collapse, to $$M_{\alpha}$$.