There's two ideas that I've been thinking about for Delirium.

Delirium as a cooldown.
- DRK casts Delerium, absorbing the first damage instance that DRK takes. DRK is given a buff called Nemesis. During Nemesis, DRK will have a 10% damage buff for 15 seconds. After 15 seconds, if DRK did no damage, he will take the full damage Delirium has absorbed. Dealing damage will reduce the damage Delirium will deal after 15 seconds.
- Example
1. DRK casts Delerium. DRK takes 15k damage.
2. DRK gets Nemesis. DRK deals 8k damage.
3. DRK receives 7k damage. (15k - 8k)

Delirium as a component of TBN.
1. When TBN shield breaks, DRK will gain a charge of Nemesis and said charge will absorb the damage received by TBN.
2. Each charge of Nemesis will also give DRK a 0.1% vuln up.
3. DRK can cast Delerium whnever DRK has at least one charge of Nemesis.
4. Upon casting Delirium, DRK will deal ddamage equal to total damage received by TBN, added by x% (x = how many Nemesis charges DRK has) of total damage.

Example:
1. DRK breaks TBN 8 times. Each instance deals 2k damage. Total damage received via TBN is 16k.
2. DRK now has a 0.8% vuln up debuff.
3. Upon casting Delirium, DRK deals 17280 total damage. [16000 + 1280 (8% of 16k)]