If you dont mind venturing into the other two Dungeons and staying away from Tomb of Annihilation, you get to repeatedly venture into the Dungeon
Bloodmoon Ursaluna ex Special Illustration Rare 216/167 This distinctive mark has earned it the name Bloodmoon Beast, and it is the only such Ursaluna known to exist
Penumbra Bobcat When this creature dies, create a 2/1 black Cat creature token
Metamorphosis Fanatic (DSC) $39.99 You may not be aware of Metamorphosis Fanatic, never mind not realizing that its the most expensive card in Duskmourn , but its only a Commander precon exclusive (in the Miracle Worker deck if youre interested)
While Happily Ever After and Planewide Celebration are our main lifegain spells, getting a bit of extra life from Hydroid Krasis certainly doesn't hurt
In the final confrontation, he makes a connection to Gallifrey and the Time Lords grant him a new cycle of regenerations (and thus the strength to defeat the Daleks)