Hold Portal (1st Level Utility)

Ranged spell

You cast this spell on a door. For ten minutes, adventurer-tier creatures can't get through the door. Champion-tier creatures can batter it down; each attempt requires a DC 20 Intelligence skill check (including an applicable background) by the caster to resist the battering and keep the spell going. Epic-tier creatures can walk right through.

3rd Level Spell: 
The spell now lasts for an hour. Adventurer-tier creatures are stymied. Champion-tier creatures can batter the door down or destroy it after three failed DC 20 skill checks by the spellcaster. Epic creatures notice that the now-busted door had magic on it
5th Level Spell: 
Champion-tier creatures take a few minutes to force the door open. Epic creatures can force it open after one failed DC 25 skill check by the spellcaster.
7th Level Spell: 
Champion-tier creatures are stymied for up to an hour by the door. Epic tier creatures get through after three failed DC 25 skill checks by the spellcaster.
9th Level Spell: 
Champion-tier creatures can't enter. Epic-tier creatures can't get through for an hour.