So, I just blew 8 gems on the final floor of the tower. Started it off, and Estia appears on level 3. Get her down to 20% or so and she takes me from 100% health to dead, quite the shock. I figure blowing one gem is worth it so I go ahead and rez. Of course I wasn't expecting her to heal 50% when I "killed" her, but I still managed to get her down with most of my team alive and items in tact. Low and behold, she drops so of course I'm excited and figure spending that gem was worth it.
Two levels later, she appears again. I groan but since she dropped I figure I'll go on. Of course this time my luck isn't as good and my items start to run out so it takes me 2 gems to finally finish her off.
Two more levels, and there she is again. Dear god. Of course at this point I've got 3 gems spent and the drop so I'm too invested to give up (yeah, gambler's trap right there). Push through, spending 3 more gems this time. And she drops again. Get through rounds 8 and 9 but of course she's the final boss (I assume that's always the case). My items are long gone and my luck is bad so it takes me 3 more gems to finish her off. Only had one left at that point and was worried I'd run out of gems before finishing it, if that had happened I probably would have deleted and never come back.
Getting that one gem reward at the end was pretty funny considering all I spent. Oh and the two drops? A lord and a guardian of course. But at least I have her and never have to go back to that tower.