Hydra

Summons a multi-headed beast of flame to reduce your enemies to ashes.

Hydra is a Sorceress Fire skill (level 30, requires Enchant). It summons a three-headed hydra that cannot be attacked and spits fire bolts at anything in range for ten seconds. The numbers that decide it are the bolt damage, 150–175 at level 20 before synergies, the fixed 10-second duration and the cap of 6 hydras at once.

The numbers

The bolt damage comes from the EMin/EMax columns, halved by HitShift 7. The minimum starts at 14 and grows +5.5 a level to level 8, +7.5 to 16, +9.5 to 22, +11.5 to 28 and +13.5 a level past that; the maximum starts at 19.5 and grows +6.5, +8.5, +10.5, +12.5 and +14.5 in the same brackets. That is 67–82 at level 10, 150–175 at level 20 and 265–300 at level 30. The line reads lvl, so +skills count.

Two lines never change and are not in the table above. Duration is calc1 ln12: Param1 250 frames and Param2 0 a level, so 10 seconds at every level. The cap is Param3 18 ÷ 3 = 6 hydras (the table's comment: the oldest is removed when the limit is hit; the tooltip reads par3/3, three heads to a hydra).

Mana is 20 at level 1 and 0.5 more a level (mana 40, lvlmana 1, manashift 7): 29.5 at level 20. The row has no casting delay column; the Basin's page notes the 1.6-second delay of LoD is gone in D2R.

How it works

Hydra is a summon (summon "hydra1", pet type "hydra"), placed at the point you cast on, that fires the skill "HydraMissile" at your Hydra level (sumskill1, calc lvl). The bolts are fire damage, reduced by the target's fire resistance, see Dealing Elemental Damage and Resistances and Immunities; as spell missiles they need no attack rating.

The row explains why a Hydra scales like a spell and not like a pet: its passivestat columns copy the caster's passive_fire_mastery, passive_fire_pierce and item_pierce_fire_immunity onto the hydra (each as stat(…).accr), so your Fire Mastery, your Enemy Fire Resistance Reduction and a sundered fire immunity all apply to its bolts. The Basin's page says the same, and that the synergy bonuses from your skills apply too; sumskill2 and sumskill3 pass your Fire Bolt and Fire Ball hard points to the hydra for that purpose.

The Basin's page gives the shape of the thing: each of the three heads fires independently, so one hydra can shoot three targets; bolts reach about 14 2/3 yards and the heads notice targets slightly further off; the attack animation is 12 frames and cannot be sped up or slowed, with a 15-frame AI delay between shots, so the three heads together fire about 22 bolts in their 10 seconds. A hydra cannot be targeted by hostile units and simply expires. Cast one at the edge of the screen or around a corner and it fires on what you cannot see.

Synergies and +skills

• Fire Bolt: +3% fire damage per level and Fire Ball: +3% fire damage per level (skills.txt Param8 = 3; the calc reads skill('Fire Bolt'.blvl) and skill('Fire Ball'.blvl), hard points only).
• Hydra feeds nothing.
• The damage line reads lvl; the duration and the cap read nothing and never move.

Against players

A Hydra is a pet, and the difficulty table cuts a pet's hit on a player to 17% of its value, the same figure as a player's own hit (difficultylevels.txt PlayerDamagePercentVSPlayer), see Player versus Player. The Basin's page notes the Council Members' Hydra applies 17% damage to players for the same reason, and gives no other rule.

Build notes

• The synergies are the weakest in the tree (+120% from 40 hard points); Fire Mastery's +163% at level 20 and +skills do more for the bolt than Fire Bolt and Fire Ball points, which are better spent for Fire Ball's sake.
• Six hydras at 29.5 mana each is 177 mana for a full set that lasts 10 seconds; with no casting delay the set can be laid in a few seconds.
• The hydra fires at level lvl, so every +skill raises its bolts; nothing but hard points in Fire Bolt and Fire Ball changes the synergy.