I like the idea of opening said "portals" to let demons run through that are hostile to both the summoner and enemies.
Could be something similar as the Shaman in Shadowrun ; when opening the portal, there's an AP cost / turn (that increases each turn) that the player has to spend on the said portal to keep control of it (and its minions).
I wouldn't enjoy using let's say a source skill with 3-4 ap cost to open a portal and the said demon instantly attacks and disables my glass canon character the next turn...
You come back just to disagree with me aye? :P Shadowrun-like control could work. If the demons were hostile to everyone, you'd just have to be smart about where you put the portal. Maybe make the demons just attack closest targets. Summoner would be able to use any of his summon skills on them (and trust me, there will be some cool ones :D)
Or maybe by portal, they mean "Portal" portals, where you can walk and cast spells through two portals. That would be so awesome.
So to me it seems an Incarnate is like a ward in DOS (i.e. absorbs some element). A totem is a summon (perhaps like the creature in DKS) - something that attacks as well. Is that right?
It appears to me that the incarnate is your standard summon that can move around and attack, but whatever surface you summon it in changes its element type. Don't know if it "asborbs" the surfaces or not.
The totem appears to be a non-moving summon that you can't control and automatically attacks nearby enemies, while also probably providing some kind of aura that affects enemies or allies.
Neither summon-type is overtly defensive or offensive, with different strengths and weaknesses. It's a clever way to allow multiple summons at once, though the first screenshot on the page shows 3 totems at once with a 2-member party, only 1 which appears to have summoning. Pretty surprising to be able to summon at least 3 totems at once.